This service manual is designed to provide comprehensive information and procedures for the maintenance, repair, and overhaul of the John Deere 8520T tractor. It serves as an indispensable resource for qualified technicians and mechanics who are responsible for ensuring the optimal performance, reliability, and longevity of this sophisticated agricultural machine. The manual encompasses a wide range of topics, from basic servicing tasks to complex diagnostic and repair procedures, empowering users to effectively address any issues that may arise during the tractor's operational lifespan. Proper use of this manual will contribute significantly to minimizing downtime, maximizing productivity, and extending the overall service life of your John Deere 8520T.
The information contained within this manual is intended to be used in conjunction with sound mechanical principles and recognized industry practices. While every effort has been made to ensure the accuracy and completeness of the information presented, John Deere reserves the right to make changes and improvements to the tractor and the manual itself without prior notice. Technicians are encouraged to stay updated on the latest service bulletins and technical communications released by John Deere to ensure they are employing the most current and accurate procedures. Furthermore, it is crucial that all repairs are performed by qualified personnel with the appropriate tools and equipment to prevent damage to the tractor and ensure the safety of the technician.
Proper identification of your John Deere 8520T tractor is crucial for accurate diagnosis and repair. The model number and serial number are typically located on a plate affixed to the tractor's frame, often near the front axle or on the left side of the engine compartment. This information is essential for ordering the correct replacement parts and accessing the specific service information relevant to your particular tractor configuration. Always refer to the model and serial number when communicating with John Deere dealerships or parts suppliers to ensure you receive the correct parts and service information.
The John Deere 8520T boasts a robust set of specifications that contribute to its exceptional performance in the field. The engine, a powerful diesel powerplant, delivers significant horsepower and torque for demanding agricultural tasks. Understanding the engine's specifications, such as displacement, compression ratio, and fuel system type, is crucial for proper maintenance and troubleshooting. Key specifications for other components, such as the transmission, hydraulic system, and electrical system, are also detailed in this manual, providing a comprehensive overview of the tractor's capabilities and operational parameters.
Safety is paramount when performing any maintenance or repair work on the John Deere 8520T tractor. This section of the manual highlights crucial safety precautions and warnings that must be observed at all times to prevent personal injury and damage to the equipment. Before commencing any work, carefully read and understand all safety warnings outlined in this manual and in any other relevant documentation. Always wear appropriate personal protective equipment (PPE), such as safety glasses, gloves, and hearing protection, when working on the tractor.
Never work on the tractor while the engine is running unless specifically instructed to do so in the service procedures. Ensure the tractor is properly supported with jack stands or other suitable supports before working underneath it. Always disconnect the battery before working on the electrical system to prevent accidental shocks or short circuits. Be extremely cautious when working with pressurized systems, such as the hydraulic system and fuel system, and always relieve pressure before disconnecting any lines or fittings. By adhering to these safety precautions and warnings, you can minimize the risk of accidents and ensure a safe working environment.
The engine is the heart of your John Deere 8520T, and proper removal and installation are critical to its longevity and performance. Before beginning any removal process, ensure the tractor is parked on a level surface, the parking brake is engaged, and the wheels are properly chocked. Disconnect the battery cables, starting with the negative terminal, to prevent any electrical shorts during the process. Thoroughly clean the engine and surrounding area to avoid introducing contaminants into the engine or hydraulic systems once the engine is removed. Gathering the right tools and a detailed list of the tasks at hand will minimize issues and prevent damages during the removal.
Begin by disconnecting all hoses, wires, and linkages connected to the engine. Carefully label each component as you disconnect it; taking photographs can be invaluable for reassembly. Drain all fluids from the engine, including coolant, engine oil, and fuel. Disconnect the exhaust system from the engine manifold. Unbolt any engine shrouds or covers that might obstruct the engine's removal. Support the engine with an appropriate engine hoist or lifting device, ensuring the weight is evenly distributed. Consult the John Deere 8520T service manual for specific lifting points and torque specifications. Proper lifting of the engine is key to preventing serious injury and major damages to the components involved.
Once the engine is securely supported, disconnect it from the tractor frame. This typically involves removing mounting bolts and potentially disconnecting the transmission. Gradually lift the engine, carefully checking for any remaining connections or obstructions. Once the engine is clear of the frame, slowly and carefully maneuver it to a safe location for servicing or replacement. Installation is essentially the reverse of the removal process, ensuring all connections are properly secured, fluids are replenished, and the engine is correctly aligned with the transmission. Proper lubrication of key components like transmission input shafts will aid the final installation and prevent premature wear.
The cylinder head is a complex component housing critical parts such as valves, springs, and rocker arms. Regular cylinder head maintenance ensures proper engine compression and performance. Before beginning cylinder head service, thoroughly clean the exterior to prevent debris from entering the combustion chambers or oil passages. Carefully inspect the cylinder head for any signs of cracking, warping, or corrosion. These issues can significantly impact engine performance and may require cylinder head replacement. Make sure you have all the necessary tools, including valve spring compressors, valve seat grinders, and torque wrenches before you take on the repair.
Begin by removing the valve cover and carefully inspecting the valve train components, including valves, springs, rockers, and pushrods. Check for wear, damage, or excessive play. Use a valve spring compressor to remove the valves, taking care to keep each valve with its corresponding seat to maintain proper sealing. Inspect the valve seats for wear or damage. Lapping the valves to the seats can improve sealing and restore compression. Replace any worn or damaged valve guides, seals, or springs. It is also a good practice to replace any worn or damaged rockers and pushrods.
Before reassembling the cylinder head, thoroughly clean all components and ensure all oil passages are clear. Lubricate valve stems and guides with engine oil during reassembly. Install the valves and valve springs using a valve spring compressor. Adjust valve lash according to the John Deere 8520T service manual specifications. Improper valve lash can lead to poor engine performance, increased wear, and potential engine damage. When installing the cylinder head back onto the engine block, use a new head gasket and tighten the head bolts to the specified torque in the correct sequence. Failure to do so can result in leaks or cylinder head warping.
The fuel system is essential for delivering the correct amount of fuel to the engine. Problems with the fuel system can lead to poor performance, starting issues, or even engine damage. Regular maintenance and proper diagnostics are critical. Begin by checking the fuel filter for contamination or clogs. A clogged fuel filter can restrict fuel flow and cause the engine to run lean. Inspect the fuel lines and connections for leaks or damage. Replace any damaged or deteriorated fuel lines to prevent fuel leaks and ensure proper fuel delivery.
Check the fuel pump for proper operation. A weak or failing fuel pump may not deliver enough fuel to the engine, resulting in poor performance. Use a fuel pressure gauge to measure the fuel pressure at the fuel rail or carburetor. Compare the fuel pressure reading to the specifications in the John Deere 8520T service manual. If the fuel pressure is low, replace the fuel pump. Inspect the injectors or carburetor for proper operation. Clogged or malfunctioning injectors can disrupt fuel delivery and cause engine misfires or poor fuel economy. It is also important to check the fuel tank for debris, rust, or water contamination.
If the fuel system is equipped with electronic components, such as fuel injectors or a fuel injection control module, use a diagnostic tool to check for fault codes. Fault codes can provide valuable information about the specific problem with the fuel system. Consult the John Deere 8520T service manual for the correct diagnostic procedures and troubleshooting steps. When replacing any fuel system components, use only genuine John Deere parts or equivalent aftermarket parts. Inferior parts may not meet the required specifications and could cause further damage to the fuel system or engine.
The cooling system is vital for maintaining the engine at the correct operating temperature. Overheating can lead to severe engine damage, including warped cylinder heads, cracked blocks, and seized pistons. Regular cooling system maintenance is therefore essential. Start by checking the coolant level in the radiator and expansion tank. Add coolant as needed to maintain the correct level. Use the specified type of coolant for the John Deere 8520T; mixing different types of coolant can lead to corrosion and reduced cooling efficiency. It is also important to monitor the coolant for contamination and look for signs of rust, oil, or debris in the fluid.
Inspect the radiator and coolant hoses for leaks, cracks, or damage. Replace any damaged hoses to prevent coolant loss and ensure proper cooling system pressure. Check the radiator fins for debris or obstructions that could reduce airflow. Clean the radiator fins with compressed air or a soft brush to improve cooling efficiency. Inspect the water pump for leaks or unusual noises. A failing water pump may not circulate coolant effectively, leading to overheating. If the water pump is suspected to be faulty, replace it with a new or remanufactured unit.
The thermostat controls the coolant temperature and regulates coolant flow through the radiator. A faulty thermostat can cause the engine to overheat or run too cold. Test the thermostat by placing it in a pot of hot water and observing its operation. The thermostat should open at the specified temperature. Replace the thermostat if it is not functioning correctly. Periodically flush the cooling system to remove deposits and contaminants. Use a cooling system cleaner to dissolve deposits and then flush the system with clean water. Refill the cooling system with the correct type and concentration of coolant.
The lubrication system ensures that all moving parts within the engine are properly lubricated, reducing friction and wear. Proper lubrication is critical for engine longevity. An overhaul of the lubrication system might be necessary in instances of severe engine wear or contamination. Before beginning any lubrication system overhaul, thoroughly clean the engine exterior. Drain the engine oil and remove the oil pan. Inspect the oil pan for sludge, debris, or metal shavings. These findings can indicate internal engine problems. It is also critical to properly dispose of the old oil once the system has been drained.
Remove the oil pump and inspect it for wear, damage, or excessive play. A worn oil pump may not provide sufficient oil pressure, leading to inadequate lubrication. Replace the oil pump if necessary. Clean the oil pump screen and filter to remove any debris or contaminants. Inspect the oil passages in the engine block and cylinder head for obstructions. Use compressed air to blow out any blockages. Check the oil pressure relief valve for proper operation. A faulty relief valve can cause excessive or insufficient oil pressure.
Reassemble the lubrication system with new gaskets and seals. Install the oil pump and torque the mounting bolts to the specified value. Replace the oil filter with a new one. Install the oil pan and tighten the bolts to the specified torque. Refill the engine with the correct type and amount of engine oil. Start the engine and check the oil pressure gauge to ensure that the oil pressure is within the specified range. Monitor the engine for any leaks or unusual noises. Always refer to the John Deere 8520T service manual for specific torque specifications and maintenance procedures.
Understanding the wiring diagrams and schematics for the John Deere 8520T is crucial for effective troubleshooting and repair of the electrical system. These diagrams provide a visual representation of the electrical circuits, showing the location of components, wiring connections, and protective devices like fuses and circuit breakers. Always refer to the correct diagram specific to your tractor's serial number or model year, as variations can exist even within the same model line. Mastering the ability to interpret these diagrams allows you to trace circuits, identify potential faults, and perform accurate voltage and continuity testing. Before performing any electrical work, disconnect the battery to prevent accidental shorts or damage to sensitive electronic components. Remember, safety is paramount when working with electrical systems.
The schematics often use symbols to represent different electrical components. Familiarize yourself with the standard symbols for resistors, capacitors, diodes, transistors, relays, switches, and other electrical devices. These symbols are consistent across most electrical diagrams, making it easier to understand the circuit's function at a glance. Furthermore, the diagrams typically include wire color codes, which are essential for identifying specific wires within a harness. Knowing the wire color and its corresponding function is extremely helpful when tracing circuits and troubleshooting wiring problems. Don't hesitate to consult the legend or key that accompanies the wiring diagram to decode the symbols and wire colors accurately.
A malfunctioning starting system can prevent your John Deere 8520T from operating. Common issues include a weak battery, faulty starter motor, defective solenoid, or wiring problems. Begin by inspecting the battery terminals for corrosion and ensuring they are securely connected. Check the battery voltage with a multimeter; a fully charged battery should read approximately 12.6 volts. If the battery voltage is low, charge the battery or replace it if necessary. Next, examine the starter motor and solenoid for physical damage or loose connections. A common test is to check for voltage at the solenoid when the key is turned to the start position. If there's no voltage, trace the wiring back to the ignition switch and check for continuity.
If the solenoid receives voltage but the starter motor does not engage, the solenoid itself may be faulty. You can test the solenoid by bypassing it with a jumper cable; carefully connect the jumper cable directly to the starter motor's positive terminal. If the starter motor cranks, the solenoid is likely the problem. If the starter motor still doesn't engage, it could be a problem within the starter motor itself. In this situation, removing the starter motor for bench testing and potential rebuilding is advised. Always remember to disconnect the battery before working on the starter system to prevent accidental shorts and potential injuries.
The charging system is vital for maintaining the battery's charge and providing power to the tractor's electrical components while the engine is running. A faulty charging system can lead to a dead battery and prevent the tractor from starting. Start by visually inspecting the alternator for any signs of damage, such as cracked housing or loose wires. Check the belt tension and condition; a loose or worn belt can prevent the alternator from spinning at the correct speed, reducing its output. Use a multimeter to measure the voltage at the battery terminals while the engine is running. A properly functioning charging system should produce a voltage between 13.5 and 14.5 volts.
If the charging voltage is outside the acceptable range, further diagnosis is required. Check the alternator's output voltage directly at the alternator terminals. If the alternator output is low, it may need to be rebuilt or replaced. Also, inspect the wiring between the alternator, battery, and voltage regulator for any signs of damage or corrosion. A poor connection can create resistance and reduce the charging system's efficiency. The voltage regulator plays a crucial role in controlling the alternator's output and preventing overcharging. If you suspect a faulty voltage regulator, test it according to the manufacturer's specifications. Remember to consult the service manual for detailed testing procedures and troubleshooting tips.
Properly functioning lights and a clear instrument panel are essential for safe and efficient operation of the John Deere 8520T. Faulty lights can reduce visibility, especially during nighttime operation, while a malfunctioning instrument panel can prevent you from monitoring critical engine parameters. Begin by checking the fuses for the lighting and instrument panel circuits. A blown fuse is often the culprit for non-functioning lights or gauges. Replace the fuse with one of the correct amperage rating. If the fuse blows repeatedly, there's likely a short circuit in the wiring. Inspect the wiring harness for any signs of damage or chafing.
For instrument panel issues, start by checking the connections to the gauges and sensors. Loose or corroded connections can cause inaccurate readings or complete failure. Clean the connections with a wire brush and apply dielectric grease to prevent corrosion. If a specific gauge is malfunctioning, test the corresponding sensor according to the service manual's instructions. A faulty sensor can provide incorrect data to the gauge. To troubleshoot light failures, check the bulb's condition and the socket for corrosion. Replace any burned-out bulbs and clean the socket terminals. Use a test light to check for power at the socket when the light switch is activated. If there's no power, trace the wiring back to the switch and check for continuity.
Many functions of the John Deere 8520T are controlled by electronic control units (ECUs) that rely on sensor inputs to make decisions. Accurate sensor readings are critical for optimal performance and fuel efficiency. Periodically, these controllers and sensors may require calibration to ensure they are providing accurate data. The calibration process typically involves using a diagnostic tool to communicate with the ECU and adjusting the sensor parameters to match the actual physical conditions. Consult the service manual for the specific calibration procedures for each sensor and controller.
Before performing any calibration, ensure that the sensors are properly installed and functioning within their specified range. Check the wiring connections for any signs of damage or corrosion. Use a multimeter to verify the sensor's output voltage or resistance. If a sensor is not functioning correctly, it may need to be replaced before calibration. Improper calibration can lead to performance issues, such as erratic engine behavior or inaccurate hydraulic system control. Always follow the manufacturer's instructions carefully during the calibration process. Document the initial sensor values before making any adjustments. This information can be helpful if you need to revert to the original settings. After completing the calibration, verify the sensor readings and monitor the tractor's performance to ensure that the adjustments have improved its operation.
The power train of your John Deere 8520T is a complex system of components working together to transfer engine power to the tracks, enabling the tractor to perform its intended tasks. This system includes the transmission, differential, final drives, hydraulic system (crucial for shifting and control), and the power take-off (PTO). Regular maintenance and timely repairs are essential to keep this system operating at peak efficiency and prevent costly downtime. Neglecting the power train can lead to reduced performance, increased fuel consumption, and ultimately, major component failures. This chapter will provide detailed information on servicing, repairing, and troubleshooting the key components of the 8520T's power train, allowing you to keep your machine in top working condition. Understanding each section and the recommended procedures outlined in this manual is crucial for any technician working on this powerful machine.
The transmission is the heart of the power train, responsible for converting the engine's power and torque into usable force for different operating conditions. It allows the tractor to operate at various speeds and pull different loads effectively. Regular transmission service is vital, including fluid level checks, filter replacements, and visual inspections for leaks or damage. Low fluid levels can lead to overheating and premature wear of internal components, while contaminated fluid can cause abrasive damage and reduced performance. Always use the recommended John Deere Hy-Gard fluid to ensure proper lubrication and prevent damage to seals and other components. Proper shifting techniques are also important to extend the life of the transmission.
When performing a transmission fluid change, be sure to follow the recommended procedure in this manual. This includes draining the old fluid, replacing the filter, and filling the transmission with the correct amount of new Hy-Gard fluid. Overfilling or underfilling can both be detrimental to the transmission's performance. Furthermore, inspect the transmission cooler for any debris or obstructions that could restrict airflow and lead to overheating. Clean the cooler as needed to maintain optimal cooling performance. During the service process, pay close attention to the drained fluid for any signs of metal shavings or other contaminants, which could indicate internal wear or damage.
The differential and final drives work together to transfer power from the transmission to the tracks, allowing for smooth and efficient turning. The differential allows the wheels to rotate at different speeds during turns, preventing wheel slippage and damage. The final drives provide a further reduction in gear ratio, increasing torque at the tracks. These components are subjected to high stress and require regular inspection and maintenance. Check for leaks around the seals and bearings, and inspect the gears for wear or damage. Any unusual noises or vibrations coming from the differential or final drives should be investigated immediately. Ignoring these symptoms can lead to catastrophic failure and expensive repairs.
When repairing the differential or final drives, always use genuine John Deere parts to ensure proper fit and performance. The use of aftermarket parts can compromise the reliability and durability of the system. Pay close attention to the torque specifications when reassembling these components, as improper torque can lead to premature failure. Furthermore, ensure that all seals and gaskets are in good condition and properly installed to prevent leaks. After completing the repair, check the fluid level in the differential and final drives and top off as needed. Regularly scheduled oil analysis can also help you monitor the condition of these components and identify potential problems before they become major issues.
The hydraulic system plays a crucial role in the operation of the 8520T, controlling functions such as shifting, steering, and implement control. A properly functioning hydraulic system is essential for smooth and efficient operation. Troubleshooting hydraulic problems can be challenging, but with a systematic approach and the proper tools, most issues can be resolved. Start by checking the fluid level and condition, looking for signs of contamination or air bubbles. Check the hydraulic lines and hoses for leaks or damage. Use a pressure gauge to check the system pressure at various points, comparing the readings to the specifications in this manual. Inspect the hydraulic pumps and valves for proper operation.
When troubleshooting hydraulic problems, it is important to follow a logical process of elimination. Begin with the simplest and most likely causes, such as low fluid level or a clogged filter, and then proceed to more complex issues, such as a faulty pump or valve. Use the diagnostic charts in this manual to help pinpoint the source of the problem. Always relieve the pressure in the hydraulic system before disconnecting any lines or components. Use caution when working with hydraulic fluid, as it can be under high pressure and can cause serious injury if it comes into contact with the skin. Ensure the hydraulic system is regularly inspected and maintained, following the service schedules provided, can greatly extend the system’s overall life.
The Power Take-Off (PTO) system is used to transmit power from the engine to implements such as mowers, balers, and tillers. Proper PTO system maintenance is crucial for safe and efficient operation. Regularly inspect the PTO shaft and driveline for wear, damage, or missing parts. Check the PTO shield for damage and ensure that it is securely in place. Lubricate the PTO shaft and driveline according to the manufacturer's recommendations. Engage and disengage the PTO slowly and smoothly to prevent shock loading and damage. Always disengage the PTO and shut off the engine before servicing or adjusting any implements.
When performing PTO system maintenance, pay close attention to the condition of the U-joints and slip joints on the PTO shaft. These components are subjected to high stress and require regular lubrication. Replace any worn or damaged parts immediately to prevent failure. Ensure that the PTO speed is set correctly for the implement being used, as operating at the wrong speed can damage both the PTO system and the implement. Prioritize safety when operating any PTO driven implement. The driveline should always be adequately shielded. Understand the safety procedures before engaging. Following these guidelines will keep you safe and help ensure your PTO system is functioning as intended.
The hydraulic pump in your John Deere 8520T is the heart of the entire hydraulic system. It's responsible for generating the pressure and flow required to operate everything from the steering to the implements. Because of its vital role, proper maintenance and timely service are crucial to prevent costly breakdowns. Regularly inspect the pump for any signs of leaks, unusual noises, or vibrations. These symptoms can indicate worn seals, damaged bearings, or internal component failure. Ignoring these warning signs can lead to a complete pump failure, leaving you stranded in the field.
When servicing the hydraulic pump, begin by relieving the system pressure according to the safety procedures outlined in this manual. Disconnect the hydraulic lines carefully, plugging them to prevent contamination. Thoroughly clean the pump exterior before disassembly to prevent dirt and debris from entering the internal components. Use only genuine John Deere replacement parts during reassembly, ensuring proper fit and performance. Always torque bolts to the manufacturer's specifications, and double-check all connections for tightness before refilling the hydraulic system. Proper priming of the pump is essential after reassembly to prevent cavitation and damage.
The valve bank controls the flow of hydraulic fluid to various actuators, such as cylinders and motors. Malfunctions in the valve bank can lead to erratic operation, reduced power, or complete failure of hydraulic functions. Diagnosing valve bank problems requires a systematic approach, starting with a visual inspection for leaks, damage, or loose connections. Use a hydraulic pressure gauge to check system pressure at various points in the valve bank to identify pressure drops or restrictions. Compare readings to the manufacturer's specifications to pinpoint the source of the problem.
Often, sticking valves are the cause of valve bank issues. Contamination within the hydraulic fluid can lead to valve sticking. Inspect the hydraulic fluid for contaminants. Clean the system if needed. Solenoid valves can also fail due to electrical problems. Use a multimeter to check the solenoid coil resistance and voltage supply. Replace any faulty solenoids or wiring as necessary. When disassembling the valve bank, keep all components organized and clean to prevent damage or contamination during reassembly. Properly torque all bolts to the manufacturer's specifications and use new seals or O-rings when reassembling to prevent leaks.
Hydraulic cylinders are responsible for providing linear motion to various machine components, such as the steering mechanism and implement lift arms. Over time, cylinders can develop leaks due to worn seals or damaged rods. External damage to the cylinder barrel can also compromise its integrity. Repairing or rebuilding cylinders is a cost-effective alternative to replacement, but it requires careful attention to detail. Begin by thoroughly cleaning the cylinder exterior and securely mounting it in a vise. Carefully disassemble the cylinder, taking note of the order and orientation of the internal components.
Inspect the cylinder rod for scratches, dents, or corrosion. Minor imperfections can be polished out, but severely damaged rods will need to be replaced. Examine the cylinder barrel for scoring or wear. Honing the barrel can restore its surface finish, but excessive wear may necessitate replacement. Replace all seals, O-rings, and wear bands during reassembly, using only genuine John Deere replacement parts. Lubricate all components with hydraulic fluid before reassembling the cylinder. Properly torque all bolts to the manufacturer's specifications, and pressure-test the cylinder after reassembly to ensure it is leak-free.
Hydraulic motors convert hydraulic energy into rotary motion, powering components such as fan drives and auxiliary equipment. Regular maintenance is crucial to ensure optimal performance and prevent premature failure. Inspect the motor for leaks, unusual noises, or vibrations. These can indicate worn bearings, damaged seals, or internal component wear. Check the hydraulic fluid for contamination, as dirty fluid can accelerate wear and damage to the motor's internal components. Change the hydraulic fluid and filter regularly according to the manufacturer's recommendations. Regularly inspect the motor housing and hydraulic lines to ensure the components are not damaged.
When servicing the hydraulic motor, begin by relieving the system pressure according to the safety procedures outlined in this manual. Disconnect the hydraulic lines carefully, plugging them to prevent contamination. Thoroughly clean the motor exterior before disassembly to prevent dirt and debris from entering the internal components. Use only genuine John Deere replacement parts during reassembly, ensuring proper fit and performance. Always torque bolts to the manufacturer's specifications, and double-check all connections for tightness before refilling the hydraulic system. After reassembly, carefully check for leaks and confirm proper motor operation.
The John Deere 8520T relies on a robust hydraulic steering system to ensure precise control and maneuverability, especially important in demanding agricultural environments. A comprehensive overhaul of this system necessitates a meticulous approach, beginning with a thorough inspection of all components, including the steering cylinder, hydraulic pump, control valve, and connecting lines. Look for signs of wear, such as leaks, cracks, or corrosion, as these can significantly impact the system's performance and reliability. Prior to disassembly, carefully note the orientation and placement of each part to facilitate accurate reassembly later on.
Disassembly should be performed in a clean, well-lit environment to prevent contamination of sensitive hydraulic components. Use appropriate tools to avoid damaging fittings or seals. The steering cylinder, a critical component, requires careful attention during overhaul. Inspect the cylinder bore for scoring or wear and replace seals and wipers to ensure proper sealing and prevent hydraulic fluid leakage. The hydraulic pump, responsible for providing the necessary pressure for steering, should be thoroughly inspected for impeller wear, cavitation damage, and seal integrity. Replacing worn or damaged components with genuine John Deere parts is crucial for maintaining the system's original performance and reliability.
Once all components have been inspected, repaired, or replaced, reassembly can begin. Follow the manufacturer's specifications for torque values and component alignment to ensure proper functionality. Bleed the steering system after reassembly to remove any trapped air, which can cause erratic steering behavior. After bleeding, conduct a thorough operational test to verify that the steering system is functioning correctly and providing smooth, responsive control. Check for any leaks or unusual noises and address them promptly.
Maintaining proper track tension is paramount for optimal performance and longevity of the John Deere 8520T's track system. Overly tight tracks can lead to increased wear on rollers, idlers, and the tracks themselves, while loose tracks can result in slippage and reduced traction. Regular track adjustment, therefore, is essential. Use the track adjustment mechanism, typically located on the front idler, to adjust the track tension to the manufacturer's specified range. This often involves adding or removing shims or adjusting a hydraulic cylinder.
Track repair is sometimes unavoidable due to the harsh operating conditions encountered in agricultural applications. Inspect the tracks regularly for signs of damage, such as cracked or broken grousers, worn guide lugs, or damaged track links. Minor grouser damage can sometimes be repaired by welding, but severely damaged grousers should be replaced. Damaged track links can weaken the entire track system and should be addressed immediately. Replacing individual track links or entire sections of track may be necessary. Be sure to use the correct replacement parts and follow the manufacturer's instructions for installation.
When replacing track components, pay close attention to the condition of the track rollers and idlers. Worn or damaged rollers and idlers can accelerate track wear and reduce overall machine efficiency. Inspect the roller bearings for signs of wear or damage and replace them as needed. Ensure that the rollers and idlers are properly lubricated to minimize friction and extend their service life. Finally, after any track adjustment or repair, always double-check the track tension and alignment to ensure optimal performance and prevent premature wear.
The undercarriage of the John Deere 8520T, comprising the tracks, rollers, idlers, and sprockets, is subjected to constant stress and wear. Regular maintenance of these components is critical for maximizing machine uptime and minimizing repair costs. A thorough inspection of the undercarriage should be performed regularly, paying close attention to the condition of each component. Look for signs of wear, damage, or misalignment.
Lubrication is a key aspect of undercarriage maintenance. Regularly lubricate all grease fittings on the rollers, idlers, and sprockets to minimize friction and prevent premature wear. Use a high-quality grease that is specifically formulated for heavy-duty applications. Proper lubrication not only extends the life of the undercarriage components but also reduces the risk of costly repairs. In addition to lubrication, cleaning the undercarriage regularly is important, too. Accumulated mud, dirt, and debris can accelerate wear and hinder proper lubrication.
The drive sprockets are a crucial part of the undercarriage. Periodically check the condition of the drive sprockets, which transfer power from the drivetrain to the tracks. Worn or damaged sprockets can cause excessive track wear and reduce the machine's overall efficiency. Replace worn sprockets promptly to prevent further damage and maintain optimal performance. Regular undercarriage maintenance, including inspection, lubrication, cleaning, and timely component replacement, is essential for maximizing the lifespan and performance of your John Deere 8520T's track system. Failing to maintain these components can lead to expensive repairs and significant downtime.
The cab of the John Deere 8520T houses all of the essential controls and instruments for operating the tractor. Properly removing and installing the cab is crucial for accessing various components beneath, such as the transmission and hydraulic systems. Always disconnect the battery before commencing any work on the cab, ensuring that all electrical circuits are de-energized. Carefully disconnect all wiring harnesses and hydraulic lines associated with the cab, labeling each connection to guarantee correct reassembly. Failure to properly label and disconnect these connections can result in damage to electrical or hydraulic systems.
Lifting the cab requires specialized equipment, such as a crane or hoist, with a sufficient weight rating to safely handle the cab's mass. Securely attach lifting straps to designated lifting points on the cab structure, ensuring even weight distribution. Carefully raise the cab, ensuring that it clears all surrounding components and obstacles. With the cab lifted, inspect the mounting surfaces for any damage or corrosion and make necessary repairs. When reinstalling the cab, align it carefully with the chassis and tighten all mounting bolts to the specified torque, ensuring a secure and stable connection. Remember to double-check all connections before energizing systems.
The air conditioning (A/C) system in the John Deere 8520T provides a comfortable operating environment for the operator, especially in hot weather conditions. Proper maintenance of the A/C system is essential for ensuring optimal performance and preventing costly repairs. Regularly inspect the A/C compressor, condenser, and evaporator for any signs of leaks, damage, or corrosion. Check the refrigerant level using a manifold gauge set and recharge the system as needed, following the manufacturer's recommendations for refrigerant type and quantity.
Clogged or dirty air filters can significantly reduce the efficiency of the A/C system and lead to poor cooling performance. Clean or replace the air filters regularly, depending on the operating environment and the manufacturer's recommendations. Inspect the A/C system's electrical components, such as the compressor clutch, fan motors, and wiring harnesses, for any signs of damage or corrosion. Perform pressure tests to confirm there is no blockage in the expansion valve or any other part of the system. Address any electrical issues promptly to prevent further damage. When working with refrigerant, always wear appropriate personal protective equipment (PPE) and follow all safety guidelines.
The operator seat and controls in the John Deere 8520T are designed to provide a comfortable and ergonomic operating experience. Proper adjustment of the seat and controls is essential for reducing operator fatigue and maximizing productivity. Adjust the seat height, fore-aft position, and lumbar support to achieve a comfortable and supportive seating posture. Ensure that the seat suspension system is functioning correctly and adjust the damping settings to match the operator's weight and preference.
Adjust the steering wheel height and tilt to achieve a comfortable reach and optimal visibility of the instrument panel. Ensure that all controls, such as the throttle, clutch, and brake pedals, are within easy reach and operate smoothly. Inspect the control linkages and cables for any signs of wear or damage and make necessary adjustments or repairs. Correct positioning and angle of the seat can drastically improve visibility and safety in difficult circumstances. Regularly lubricate the control linkages to ensure smooth and consistent operation. Familiarize yourself with all of the seat and control adjustment features and utilize them to optimize your operating experience. Also, ensure that any adjustments are firmly secured after making them to avoid unexpected movement during operation.
The instrument cluster in the John Deere 8520T provides the operator with essential information about the tractor's operating parameters, such as engine speed, fuel level, and coolant temperature. A malfunctioning instrument cluster can lead to inaccurate readings and potentially damage critical tractor components. Before attempting any repairs on the instrument cluster, consult the service manual for detailed instructions and safety precautions. Disconnect the battery before working on any electrical components.
Carefully remove the instrument cluster from the dashboard, taking note of the wiring harness connections and mounting hardware. Inspect the instrument cluster for any signs of damage, such as broken lenses, cracked housings, or corroded terminals. Check the bulbs and LEDs for any burnouts and replace them as needed. Use a multimeter to test the electrical circuits and components for continuity and voltage. If the instrument cluster requires more extensive repairs, such as replacing the circuit board or display screen, consider sending it to a qualified repair technician. Ensure that the replacement parts are compatible with the original instrument cluster.
The John Deere 8520T tractor utilizes an advanced electronic control system to manage and monitor various engine, transmission, and hydraulic functions. This system is capable of detecting and storing diagnostic trouble codes (DTCs) when a fault or anomaly is detected within the system's parameters. These DTCs can be invaluable in pinpointing the source of a problem, reducing diagnostic time, and ensuring accurate repairs. To access the diagnostic codes, use the John Deere Service ADVISOR™ diagnostic software or the tractor's CommandCenter™ display (if equipped) to navigate through the diagnostic menus. Understanding how to interpret these codes is crucial for effective troubleshooting; each code corresponds to a specific sensor, actuator, or system circuit, and the service manual provides detailed descriptions of each code's potential causes and recommended repair procedures.
When a DTC is displayed, carefully record the code number and any accompanying information, such as the frequency of occurrence or specific operating conditions present when the code was triggered. Consult the diagnostic code index in this manual to determine the component or system associated with the code. The diagnostic procedures outlined in the manual provide a step-by-step guide to isolating the fault. These procedures may involve inspecting wiring harnesses, checking sensor values, performing continuity tests, and verifying the functionality of actuators. Always follow the recommended safety precautions when working with electrical circuits and components. Never disconnect any wires or electronic components when the machine is running. Ensure all batteries and electrical power is disconnected to prevent harm to yourself and the equipment.
Troubleshooting charts are provided in this manual as a quick reference guide for common problems encountered with the John Deere 8520T tractor. These charts present a logical approach to diagnosing problems, starting with the most likely causes and progressing to more complex or less frequent issues. Each chart typically begins with a symptom or complaint, such as "Engine will not start" or "Transmission slipping." Following the chart, you'll find a series of questions or tests designed to narrow down the possible causes of the problem. Each question or test will lead you to another section of the chart or directly to a repair procedure. Pay close attention to the order of the steps and the specific instructions provided in each chart to avoid overlooking important details.
These charts are invaluable for quickly understanding the machine and the problems that may occur. The charts should be used by service technicians and mechanics to work through the troubleshooting process. It is important to note that the troubleshooting charts are not exhaustive and may not cover every possible scenario. In some cases, you may need to use your experience and knowledge of the tractor to supplement the information provided in the charts. Always refer to the detailed repair procedures in this manual for specific instructions on how to repair or replace components. Remember to always consult the most up to date version of this manual.
Component testing procedures are essential for verifying the functionality of individual parts within the John Deere 8520T tractor's systems. Before replacing a component, it's crucial to ensure that it is indeed faulty. Component testing can save time and money by preventing unnecessary replacements. These procedures typically involve using a multimeter, ohmmeter, or other specialized test equipment to measure voltage, resistance, current, or pressure at specific points on the component. Compare the measured values to the specifications provided in this manual to determine if the component is within acceptable tolerances. If the measured values are outside the specified range, the component is likely defective and should be replaced.
When performing component testing, be sure to follow the safety precautions outlined in this manual. Disconnect the tractor's battery before working on electrical components to prevent accidental shorts or electrical shocks. Use the correct test equipment for the specific component being tested and ensure that the equipment is properly calibrated. Carefully follow the instructions provided in the component testing procedures and pay close attention to the polarity of electrical connections. Record all test results and compare them to the specifications to accurately diagnose the component's condition. Always refer to the wiring diagrams and schematics in this manual to identify the correct test points and connections. Remember that a seemingly defective component may be functioning properly but receiving incorrect signals from another part of the system, so always consider the possibility of a related fault elsewhere in the tractor.
Maintaining your John Deere 8520T tractor according to the recommended service intervals is critical for ensuring optimal performance, longevity, and minimizing costly downtime. Adhering to the schedule prevents minor issues from escalating into major repairs, safeguarding your investment and maximizing productivity. Regular checks and services, performed at the specified intervals, allow for early detection of potential problems, such as worn parts, leaks, or decreased fluid levels, allowing for timely intervention and prevention of more severe damage. The service intervals are based on operating hours or calendar months, whichever comes first, and should be tracked diligently in the maintenance log. This practice not only extends the lifespan of your tractor but also contributes to safer operation and reduced fuel consumption.
The scheduled maintenance intervals encompass a wide range of tasks, including fluid checks, filter replacements, lubrication of various components, and inspection of critical systems. Engine oil and filter changes are among the most important, preventing engine wear and maintaining optimal lubrication. Hydraulic fluid and filter changes ensure smooth and efficient operation of hydraulic systems, preventing contamination and pressure loss. Transmission fluid and filter changes are vital for proper gear shifting and overall transmission performance. In addition to fluid-related tasks, scheduled maintenance also includes inspection and adjustment of belts, hoses, and other components, as well as checking and cleaning the cooling system to prevent overheating.
Proper lubrication is paramount to the smooth and efficient operation of your John Deere 8520T tractor, minimizing friction, wear, and heat buildup. The lubrication chart provides a comprehensive guide to all lubrication points on the tractor, specifying the type of lubricant recommended for each location. Following the lubrication chart diligently ensures that each component receives the correct lubricant, preventing premature wear and extending the lifespan of critical parts. Regular lubrication not only reduces friction but also helps to protect against corrosion, keeping the tractor operating at peak performance. Always consult the chart before lubricating to be sure you are following the correct steps.
The lubrication chart typically includes detailed diagrams illustrating the location of each lubrication point, along with specific instructions for applying the lubricant. Grease fittings, also known as zerks, are common lubrication points on bearings, joints, and other moving parts. It is important to use a grease gun to inject grease into these fittings until fresh grease appears, indicating that the old grease has been purged. Oil reservoirs, such as those for the engine, transmission, and hydraulics, require periodic topping off or fluid changes according to the scheduled maintenance intervals. Always use the specified type of lubricant for each application, as using the wrong lubricant can lead to damage and reduced performance. Remember that proper lubrication is an investment in the longevity and reliability of your tractor.
Maintaining the proper adjustment of various systems and components on your John Deere 8520T tractor is essential for optimizing performance, efficiency, and safety. Adjustment procedures are designed to compensate for wear, slack, or changes in operating conditions, ensuring that each component functions within its specified parameters. Correct adjustments prevent premature wear, improve fuel economy, and enhance the overall handling and responsiveness of the tractor. These adjustments are important because they are used to maintain factory settings, which allows for maximum performance and reliability of the unit.
Adjustment procedures may involve adjusting the tension of belts, calibrating control linkages, setting valve clearances, or fine-tuning fuel injection systems. Belt tension is crucial for preventing slippage and ensuring efficient power transfer from the engine to various accessories, such as the alternator, water pump, and air conditioning compressor. Control linkage adjustments ensure precise and responsive operation of the throttle, clutch, and brakes, enhancing operator control and safety. Valve clearance adjustments are vital for proper engine performance, preventing valve damage and optimizing fuel economy. Fuel injection system calibration ensures that the correct amount of fuel is delivered to the engine at all times, maximizing power output and minimizing emissions. It is recommended that you check adjustments every time you maintain the tractor.
Maintaining and repairing a John Deere 8520T tractor often requires specialized tools beyond the typical mechanic's kit. Using the correct tools not only ensures the job is done efficiently and correctly, but also prevents potential damage to the tractor's components. A comprehensive list includes, but is not limited to, a high-quality torque wrench set covering a wide range of torque values, hydraulic pressure gauges for diagnosing hydraulic system issues, and specific John Deere diagnostic tools that can interface with the tractor's electronic control unit (ECU). Accurate diagnosis and repair hinge on having these specialized instruments readily available in the maintenance bay. Neglecting to acquire the proper tools can lead to significant downtime, improper repairs, and potentially costly damage to the tractor.
Essential for engine work are compression testers, leak-down testers, and fuel injector testing equipment. The compression tester helps evaluate the engine's cylinders to see if there's any loss. On the other hand, the leak-down tester assesses the rate at which the air leaks, to check the condition of the piston rings, valves, and cylinder head gasket. Additionally, a multimeter is a necessity for electrical troubleshooting, allowing you to measure voltage, resistance, and continuity in circuits. A hydraulic jack and jack stands with sufficient weight capacity are crucial for safely lifting and supporting the tractor during undercarriage repairs. Investing in quality tools pays dividends in the long run, improving the accuracy and longevity of your repairs.
Proper use of special tools is paramount for effective and safe maintenance. For instance, when using a torque wrench, it is crucial to understand the specified torque values for each fastener. Always consult the service manual for the correct settings and follow the tightening sequence meticulously to avoid warping or damaging components. Before each use, inspect your torque wrench for wear and tear, and have it calibrated regularly to ensure accuracy. Applying excessive torque can strip threads or damage bolts, while insufficient torque can lead to loose connections and potential failures during operation.
Hydraulic pressure gauges must be connected correctly to the appropriate test ports within the hydraulic system. Refer to the hydraulic system schematics in the service manual to identify the correct ports. When taking pressure readings, ensure the tractor is operating under the conditions specified in the diagnostic procedure. Never exceed the maximum pressure rating of the gauge, as this can damage the instrument or cause a dangerous rupture. The John Deere diagnostic tools require specific software and training to operate effectively. It is recommended to undergo formal training on the use of these tools to ensure accurate data interpretation and proper troubleshooting.
In certain situations, a specific tool required for a repair may not be readily available or cost-effective to purchase. In such cases, fabricating a special tool might be a viable option. However, exercise extreme caution and only attempt fabrication if you possess the necessary skills, materials, and equipment. Always prioritize safety and adhere to established engineering principles to ensure the tool is robust and performs its intended function without risk of failure. Before starting the fabrication process, carefully study the dimensions, materials, and functionality of the original tool as described in the service manual.
When fabricating a special tool, select high-quality materials that can withstand the forces and stresses they will encounter during use. Use appropriate welding techniques and ensure all joints are strong and secure. Pay particular attention to tolerances and dimensions to ensure the fabricated tool fits properly and does not damage the components it is intended to work with. After fabrication, thoroughly test the tool in a controlled environment before using it on the tractor. If you are unsure about any aspect of the fabrication process, consult with a qualified machinist or engineer to ensure the tool is safe and effective.
Maintaining proper torque on fasteners is critical for the longevity and performance of your John Deere 8520T. Under-torqued fasteners can loosen over time, leading to component failure and potential safety hazards. Conversely, over-torquing can damage threads, distort components, and also compromise the integrity of the connection. Always consult the torque specifications listed in this section before tightening any fastener on your tractor. We provide values in both Newton-meters (Nm) and foot-pounds (ft-lbs) for your convenience. Note that specific torque values may vary depending on the fastener size, material, and application, so be sure to double-check the correct specification for the exact component you are working on. If in doubt, always err on the side of caution and consult with a qualified technician or reference the official John Deere parts catalog to verify component-specific information.
The torque specifications listed below are general guidelines and may not apply to all fasteners on your 8520T. For specific torque values related to engine components, transmission parts, or hydraulic system fittings, refer to the relevant section within this manual. Use a calibrated torque wrench to ensure accurate tightening. Make sure the torque wrench is set to the correct units (Nm or ft-lbs) and that the fastener is clean and free of debris before tightening. A lubricated fastener might require a lower torque value to achieve the same clamping force as a dry one, but this should be explicitly stated in the service procedure. Always adhere to the manufacturer’s recommendations and avoid guessing the appropriate torque value.
Below is a table listing common fastener sizes and their corresponding torque specifications. These values apply to dry, unlubricated fasteners unless otherwise specified. Remember that this is just a general guide and the exact torque value may vary depending on the specific application. When replacing fasteners, always use the correct size and grade as specified by John Deere. Substituting incorrect fasteners can compromise the structural integrity of the component and lead to premature failure. Moreover, always torque fasteners in the correct sequence, especially when assembling components with multiple bolts, to ensure even distribution of clamping force. Check the respective section of this manual for a guide or an illustration.
| Fastener Size | Torque (Nm) | Torque (ft-lbs) |
|---|---|---|
| M6 | 9 | 7 |
| M8 | 22 | 16 |
| M10 | 44 | 32 |
| M12 | 77 | 57 |
Throughout this manual, you'll encounter various units of measurement, including metric and imperial units. These units are used to measure parameters such as length, weight, pressure, temperature, and fluid volume. To facilitate accurate conversions between these units, we have included comprehensive conversion charts in this section. It is essential to use the correct units when performing measurements and calculations to ensure the accuracy of your work. Incorrect unit conversions can lead to significant errors and potentially damage components or compromise the performance of your 8520T.
The conversion charts provided below cover the most commonly used units in tractor maintenance and repair. These charts include conversions for length (millimeters to inches, meters to feet), weight (kilograms to pounds), pressure (kilopascals to pounds per square inch), temperature (Celsius to Fahrenheit), and fluid volume (liters to gallons). In addition to the charts, we also provide the formulas used to perform these conversions manually. This allows you to calculate conversions beyond the values listed in the charts. If you need to use the formula make sure to plug in the right numbers.
Always double-check the units of measurement before performing any calculations or adjustments on your tractor. Using the wrong units can lead to significant errors and potentially damage components. For example, using psi instead of bar in hydraulic pressure setting can lead to catastrophic failure. If you are unsure about the correct units to use, consult with a qualified technician or refer to the official John Deere service information. Use the tables below for reference.
| Conversion | Formula |
|---|---|
| Inches to Millimeters | Inches x 25.4 = Millimeters |
| Millimeters to Inches | Millimeters / 25.4 = Inches |
| Pounds to Kilograms | Pounds / 2.20462 = Kilograms |
| Kilograms to Pounds | Kilograms x 2.20462 = Pounds |
When repairing your John Deere 8520T, it's crucial to use the correct replacement parts. Using inferior or incompatible parts can compromise the performance, reliability, and safety of your tractor. This section provides a comprehensive parts list that includes the most commonly replaced components on the 8520T. The parts list includes the John Deere part number, a brief description of the part, and the quantity required for typical applications. It is highly recommended to utilize the official John Deere parts catalog (available online or through your local dealer) for the most up-to-date and accurate part information, as part numbers and specifications can change over time due to revisions or updates.
Before ordering any replacement parts, carefully verify the part number with the John Deere parts catalog. Also, make sure to confirm the compatibility of the part with your specific model and serial number of the 8520T. Some parts may vary depending on the year of manufacture, engine type, or other optional equipment. Ordering the wrong parts can result in delays, frustration, and potential damage to your tractor. The John Deere parts catalog often provides exploded views and diagrams that can help you identify the correct parts and their location on the machine. You can also use these diagrams as a reference during disassembly and reassembly.
The following is a sample of parts, remember to use the catalog for accurate ordering. When possible, order genuine John Deere parts to ensure optimal performance and reliability. Genuine John Deere parts are designed and manufactured to meet the stringent quality standards of John Deere and are backed by a comprehensive warranty. While aftermarket parts may be available at a lower price, they may not meet the same quality standards and can potentially damage your tractor. Keep your tractor running as if it just came out of the factory. Use the table below for the reference.
| Part Number | Description | Quantity |
|---|---|---|
| R123456 | Oil Filter | 1 |
| L789012 | Fuel Filter | 1 |
| H345678 | Air Filter | 2 |
| T901234 | Hydraulic Filter | 1 |