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John Deere 3120, 3320, 3520, 3720 - Service Engine

John Deere 3120, 3320, 3520, 3720 Engine Oil

Choose oil viscosity based on the expected air temperature range during the period between oil changes. John Deere PLUS-50 oil is recommended. TORQ-GARD SUPREME and oils meeting ACEA Specification E4/E5 may also be used. Other oils may be used if they meet one or more of the following: API Service Classification CI-4, API Service Classification CH-4, or ACEA Specification E3. Multi-viscosity diesel engine oils are preferred. Do not use break-in oils. Checking Engine Speeds - Check engine speeds when engine is warmed up and not under load. Observe tachometer.

Checking Engine Oil Level

Failure to check the oil level regularly could lead to serious engine problems if oil level is low: Check oil level before operating. Check oil level when the JD 3120, 3320, 3520, 3720 engine is cold and not running. Keep level between the Full and the Add marks. Shut off engine before adding oil. Check engine oil when engine is cold. If engine is warm, allow to cool for at least five minutes before checking oil. Park the machine safely. Dirt and contamination can enter engine when checking oil level. Clean area around dipstick before loosening or removing. Remove dipstick. Wipe with a clean cloth. Install dipstick. Remove dipstick. Check oil level on dipstick. Oil level should be between levels on dipstick. If oil level is low: Remove oil fill cap. Add proper engine oil until oil level is within operating range on dipstick. Do not overfill. Install oil fill cap. If oil is above level on the dipstick, drain to proper level. Install dipstick.

John Deere 3120, 3320, 3520, 3720 Tractors - Changing Engine Oil and Filter

Run John Deere 3120, 3320, 3520 engine to warm the oil. Park machine safely. Place drain pan under oil drain located on left side of engine. Remove drain plug. Remove two drain plugs on model JD 3720. Wipe dirt from around oil filter. Turn filter counter-clockwise to remove. Put a light coat of clean engine oil on the gasket of new filter. Install replacement oil filter by turning filter clockwise until gasket contacts filter base. Tighten additional one-half turn. Install drain plug. Do not overtighten. Install two drain plugs on model JD 3720. Remove oil fill cap. Add recommended engine oil. Install oil fill cap. Start and run engine at idle to check for leaks. Stop engine. Fix any leaks before operating. Check engine oil level and add oil if necessary.

Cleaning Rubber Dust Unloading Valve

Do not operate engine without air cleaner element and rubber dust unloading valve installed. Park the vehicle safely. Allow engine to cool. Access the engine compartment. Squeeze dust unloading valve to clean. Remove and replace if damaged. Servicing Air Filter Element - Dirt and debris can enter the engine when removing the filter element. Service filter elements only when red signal is in view in the instrument panel. Shut off engine and turn off all lights before service.

John Deere 3120, 3320, 3520, 3720 Tractor - Servicing Primary Element

Park John Deere 3120, 3320, 3520, 3720 tractor. Allow engine to cool. Check to be sure key switch and all lights are off. If the key switch or any lights are left on, the air restriction indicator light may continue to flash even after the filter has been replaced. Raise hood. Release latches and remove air cleaner canister cover. Remove and discard primary element. Clean out any dirt in canister, taking care not to damage the secondary filter element. Replace with a new primary filter element. Install air cleaner canister cover with rubber dust unloading valve pointing downward. Check instruction molded into canister cover for proper installation. Hook latches onto cover. Lower hood.

Servicing Secondary Element

Secondary element does not need routine replacement. Visually inspect it without removing from canister. Do not attempt to clean secondary element. If secondary element is replaced, install new primary and secondary element immediately to prevent dust from entering air intake system. Remove air cleaner canister cover. Remove and discard primary air filter element. Remove and discard secondary air filter element. Replace with a new secondary air filter element. Install new primary air filter element. Replace air cleaner canister cover. Lower hood. Checking Air Filter Hose - Park machine safely. Raise hood. Upper air intake flange must be properly installed into shroud adapter on radiator support frame. Locate lower air intake hose below muffler, and tighten hose clamps. Lower hood.

Checking Air Restriction Indicator Light

JD 3120, 3320, 3520, 3720 Tractor Engine exhaust fumes contain carbon monoxide. Do not run an engine in an enclosed area without adequate ventilation. Be cautious and wear protective clothing when servicing or working near a hot engine and components. Keep hands, clothing, jewelry and long hair away from moving parts. Park the machine safely. Start the engine. Raise hood. Block the air intake hose with cardboard or other solid material. Do not block with a cloth or any other material which would allow air to flow. Increase throttle to full engine rpm. The air restriction indicator light on the instrument panel should illuminate. Turn off all light switches and stop the engine. The air restriction indicator light should go out. Remove block to air intake hose and lower the hood.

John Deere 3120, 3320, 3520, 3720 Cooling System

Checking Coolant Level

Using incorrect coolant mixture can damage the radiator: Do not operate engine with plain water. Do not exceed a 50% mixture of coolant and water. Aluminum engine blocks and radiators require approved ethylene-glycol based antifreeze. If you suspect a leak, check the coolant level by removing the radiator cap and looking inside. Park the vehicle safely. Allow engine to cool. Raise hood. Check recovery tank coolant level: If engine is warm, coolant level should be between the FULL HOT line and the FULL COLD line. If engine is cold, coolant level should be at the FULL COLD line on the recovery tank. Remove recovery tank cap if necessary to add coolant. Add pre-diluted coolant or specified ratio of antifreeze and water. Install recovery tank cap. Lower hood.

John Deere 3120, 3320, 3520, 3720 Tractor Cooling System Service

Park machine safely. Allow engine to cool. Raise hood. Slowly open radiator cap to the first stop to release all pressure. Close radiator cap tightly. Position drain pan under radiator petcock on left side of machine. Open petcock and drain coolant. Disconnect coolant hose at connection to oil filter base, and allow all coolant to drain into pan. After coolant drains from the recovery tank, remove radiator cap. Close radiator petcock and connect coolant hose. Flush cooling system. Flushing Cooling System - Fill cooling system with clean water and John Deere Cooling System Cleaner, or Cooling System Quick Flush or an equivalent. Follow directions on container. Install and tighten radiator cap. Start and run engine until it reaches operating temperature. Stop engine. Open radiator petcock and disconnect coolant hose. Drain cooling system immediately before rust and dirt settle. Close radiator petcock and connect coolant hose.

John Deere 3120, 3320, 3520, 3720 Cooling System Filling

Using incorrect coolant mixture can damage the radiator: Do not operate engine with plain water. Do not exceed a 50% mixture of coolant and water. Aluminum engine blocks and radiators require approved ethylene-glycol based antifreeze. John Deere COOL-GARD coolant is recommended when adding new coolant to the cooling system. Follow the directions on the container for correct mixture ratio. Allow radiator to cool. Fill cooling system with recommended coolant. Install and tighten radiator cap. Run engine until it reaches operating temperature. Stop JD 3120, 3320, 3520, 3720 engine. Allow engine to cool. Some coolant may be drawn into the radiator from the recovery tank during cool down. Raise hood. Check recovery tank coolant level: After engine cools, coolant level should be at the FULL COLD line on the recovery tank. Remove cap rom recovery tank to add coolant if necessary. Lower hood.

Checking Radiator Hoses - Allow engine to cool. Raise hood. Check lower radiator hose for damage or cracking. Replace if necessary. Tighten hose clamps as needed. Check upper radiator hose for damage or cracking. Replace if necessary. Tighten hose clamps as needed. Lower hood.

Cleaning Radiator Screen and Fins

Raise hood. Lift and remove radiator screen off of clips on top of radiator. Clean screen with compressed air, brush or cloth, or screen may be carefully washed to remove dirt and debris. Reduced air intake can cause overheating. Keep radiator cooling fins clean. Do not use pressure washers to clean radiator cooling fins. The force produced by pressure washers will damage the radiator and cooling fins. Reduce compressed air pressure to 210 kPa (30 psi) when cleaning radiator and cooling fins. Spray compressed air straight into radiator. Do not spray radiator on an angle or cooling fins will be bent. Remove all dirt and debris from radiator fins, and fan shroud using compressed air or water. Install radiator screen. Lower hood.

John Deere 3120, 3320, 3520, 3720 - Servicing Belt

Adjusting Compressor Belt Tension

Raise hood. Apply moderate thumb pressure to belt halfway between the pulleys. Belt should deflect inward approximately 9 mm (3/8 in). Adjust belt tension if deflection is more or less than specified. Loosen nut on tensioner sheave. Slide tensioner downward for more tension on belt or upward for less tension on belt. Tighten nut on tensioner sheave and check belt tension. Adjust as necessary. Lower hood. Replacing Belt - Raise hood. Disconnect black negative (-) cable from battery. Loosen nut on tensioner sheave. Slide tensioner upward to remove tension on belt, and remove belt from compressor sheave, engine sheave, and tensioner sheave. Install new belt over engine sheave and then onto remaining sheaves. Apply pressure to tensioner sheave until tension is correct and tighten nut. Check belt tension, and adjust as necessary. Connect black negative (-) cable to battery. Lower hood.

Servicing the Alternator Belt

Allow John Deere 3120, 3320, 3520, 3720 engine to cool. Raise hood. Apply moderate thumb pressure to belt halfway between the pulleys. Belt should deflect inward approximately 9 mm (3/8 in.). Adjust belt tension if deflection is more or less than specified. Loosen top adjusting bolt: For tractors without a cab, loosen top adjusting bolt. For tractors with a cab, loosen top adjusting bolt and nut. Loosen mounting bolt. Apply outward pressure to alternator housing until tension is correct. Tighten bolts. Check belt tension. Lower hood.

Servicing Water Separator Sediment Bowl

Allow engine to cool. Red ring in bottom of sediment bowl will float on water. If ring is floating, sediment bowl should be cleaned. Check for water and deposits in sediment bowl. Clean sediment bowl and replace fuel filter if necessary. Cleaning Water Separator Sediment Bowl - Close fuel shut-off valve. Position drain pan under sediment bowl to catch fuel spillage. Turn locking collar counterclockwise to remove bowl. Remove and retain the plastic ring and spring from sediment bowl. Clean bowl, plastic ring, and spring. Install plastic ring and spring in original position in sediment bowl. Place sediment bowl and locking collar in position. Tighten locking collar to filter head to secure. Open fuel shut-off valve. Fuel system is self bleeding. Crank engine to bleed fuel system.

Cleaning Fuel Filter Sediment Bowl and Replacing Filter

Allow John Deere 3120, 3320, 3520 engine to cool. Raise hood. Close fuel shut-off valve. Position drain pan under fuel filter sediment bowl to catch fuel spillage. Turn locking collar counterclockwise to remove bowl. Remove and discard the fuel filter. Remove and retain the plastic ring and spring from sediment bowl. Clean bowl, plastic ring, and spring. Install plastic ring and spring in original position in sediment bowl. Install new filter to filter head. Place sediment bowl and locking collar in position. Tighten locking collar to filter head to secure. Open fuel shut-off valve. Lower hood. Crank engine to bleed fuel system. Replacing Fuel Filter - Allow engine to cool. Close fuel shut-off valve. Position drain pan under fuel filter to catch fuel spillage. Turn filter counterclockwise to remove and discard. Apply fuel to surface of new filter gasket. Install new filter to filter head. Tighten to one complete turn after filter contacts head. Open fuel shut-off valve.