John Deere 6068TF250 Engine

1. Warm engine to normal operating temperature.
2. When necessary, disconnect throttle linkage or cable.
3. Adjust slow idle and adjust fast idle speed when necessary.
4. Run engine at fast idle, then apply load until reaching rated speed.
5. Check power. Adjust with the screw if needed.
6. Remove load from engine.
7. Again check and adjust fast idle if the droop screw has been turned.
8. Repeat procedure until both the engine power and the fast idle speed are correct.
9. Reinstall throttle linkage if previously removed.

⚠ Valve clearance MUST BE checked and adjusted with engine COLD.

⚠ To prevent accidental starting, always disconnect NEGATIVE (—) battery terminal.

Tools: JDE83 or JD81-1 Flywheel Turning Tool, JDG1571 or JDE81-4 Timing Pin, Feeler gauge, JDG966 Crankshaft Front/Rear Rotation Adapter

1. Disconnect NEGATIVE (–) battery terminal. Remove rocker arm cover and crankcase ventilator tube.
2. Remove plugs from timing/rotation hole and timing pin hole.
3. Rotate flywheel in running direction until No. 1 cylinder is at TDC compression stroke.
4. Insert timing pin in flywheel to lock engine.
5. Check valve clearance to cold specifications.
6. Loosen jam nut on rocker arm adjusting screw; turn screw until feeler gauge slips with slight drag.
7. Hold adjusting screw and tighten jam nut to specification; recheck clearance.
8. Replace rocker arm cover and crankcase ventilator tube.

⚠ Do not pry against alternator rear frame.

Tools: JDG1341 Belt Tension Gauge

1. Install JDG1341 Belt Tension Gauge on belt halfway between pulleys.
2. Loosen cap screws (B) and (C).
3. Slide alternator or tensioner bracket in slot to remove all excess slack.
4. Stretch belt by prying outward on alternator front frame or tensioner bracket.
5. Tighten cap screws (B) and (C).
6. Run engine for ten minutes and immediately re-check belt tension per used belt specification.
7. Reset belt tension as necessary.

Tools: JDG1520 Belt Tension Tool, Torque wrench

1. Loosen upper and lower alternator bracket cap screws. Keep lower cap screw snug enough to prevent excessive play.
2. Insert JDG1520 Belt Tension Tool behind belt and over alternator mounting screw.
3. Place torque wrench on belt tensioning tool at 90° to tool. Pivot alternator until desired torque is achieved.
4. While holding tension with torque wrench, scribe a reference mark on alternator in line with notch on upper alternator bracket.
5. Continue to hold tension and tighten upper alternator bracket cap screw.
6. Check position of reference mark to see if alternator moved while tightening.
7. Remove belt tension tool and tighten lower alternator bracket cap screw.

⚠ Explosive release of fluids from pressurized cooling system can cause serious burns. Only remove filler cap when cool enough to touch with bare hands.

Tools: D05104ST Tester

1. Test radiator cap: remove radiator cap and attach to D05104ST Tester.
2. Pressurize cap to specification. Gauge should hold pressure for 10 seconds within normal range.
3. If gauge does not hold pressure, replace radiator cap.
4. Remove the cap from gauge, turn it 180°, and retest cap.
5. Test cooling system: allow engine to cool, remove radiator cap, fill radiator with coolant to normal operating level.
6. Connect gauge and adapter to radiator filler neck and pressurize cooling system to radiator cap specification.
7. With pressure applied, check all cooling system hose connections, radiator, and overall engine for leaks.
8. If leakage is detected, correct and pressure test again.

⚠ DO NOT allow thermostat or thermometer to rest against the side or bottom of container when heating water.

Tools: Thermometer, Container

1. Remove thermostat(s); visually inspect for corrosion or damage.
2. Suspend thermostat and a thermometer in a container of water.
3. Stir water as it heats; observe opening action and compare with specification.
4. Remove thermostat and observe closing action as it cools.
5. Replace any defective thermostat; on dual thermostat engine replace both.

⚠ DO NOT pressurize fuel tank to push fuel through system.

⚠ NEVER loosen screw securing pump head on Lucas rotary pumps.

Tools: Open-end wrenches

1. Loosen the air bleed vent screws two full turns by hand on fuel filter base.
2. Operate supply pump primer lever until fuel flow is free from air bubbles.
3. Tighten bleed plug securely; continue operating hand primer until pumping action is not felt.
4. Push hand primer inward toward engine as far as it will go.
5. Start engine and check for leaks.
6. If engine will not start, bleed at fuel injection pump or injection nozzles.

⚠ Use filter meeting John Deere performance specifications. DO NOT overtighten filter element.

Tools: Filter wrench

1. Run engine approximately 5 minutes to warm up oil. Shut engine off.
2. Remove oil pan drain plug and drain crankcase oil while warm.
3. Turn filter element counterclockwise with a filter wrench to remove and discard.
4. Remove oil filter packing and clean filter mounting pad.
5. Oil new packing and install new filter element; hand tighten per values on element.
6. Install oil pan drain plug with O-ring or copper washer; tighten to specification.
7. Fill engine crankcase with correct John Deere engine oil.
8. Crank engine 30 seconds without starting; run and check for leaks.

⚠ Threads on belt tensioner roller cap screw are LEFT-HAND threads.

Tools: Breaker bar and socket, Torque wrench

1. Release tension on belt using a breaker bar and socket on tension arm. Remove belt from pulleys.
2. Release tension on tension arm and remove breaker bar.
3. Put a mark on swing arm of tensioner.
4. Measure 21 mm (0.83 in.) from the mark and put a mark on tensioner mounting base.
5. Install torque wrench so that it is aligned with center of pulley and tensioner.
6. Rotate the swing arm with the torque wrench until marks are aligned.
7. Record torque wrench measurement and compare with specification. Replace tensioner assembly as required.

⚠ Only remove filler cap when engine is cold or cool enough to touch.

⚠ DO NOT add makeup oil until oil level is BELOW the add mark.

1. Check engine oil level on dipstick; add as required.
2. Check coolant level when engine is cold; level at bottom of filler neck.
3. Check single or dual fuel filters for water or debris; drain as needed.
4. Squeeze air cleaner dust unloader valve; check restriction indicator.
5. Inspect engine compartment for leaks, worn belts, loose connections and trash.

⚠ Do not run engine longer than 10 minutes while flushing. Doing so may cause engine to overheat.

1. Pressure test entire cooling system and pressure cap if not previously done.
2. Slowly open engine cooling system filler cap or radiator cap to relieve pressure.
3. Open engine block drain valve on left side of engine. Drain all coolant from engine block.
4. Open radiator drain valve. Drain all coolant from radiator.
5. Remove thermostats. Install cover (without thermostats) using old gasket; tighten cap screws to 47 N·m (35 lb-ft).
6. Close all drain valves after coolant has drained.
7. Fill cooling system with clean water. Run engine about 10 minutes to stir up rust or sediment.
8. Stop engine, pull off lower radiator hose and remove radiator cap. Immediately drain water.
9. Close drain valves, reinstall radiator cap and hose. Fill with clean water and a heavy duty cooling system cleaner such as Fleetguard RESTORE and RESTORE PLUS.
10. After cleaning, drain cleaner and fill with water to flush. Run engine about 10 minutes, then drain.
11. Close all drain valves. Reinstall radiator hose and tighten clamps. Install thermostats using a new gasket.
12. Add coolant to radiator until coolant touches bottom of filler neck. Install radiator cap.
13. Run engine until it reaches operating temperature.
14. After running engine, check coolant level and entire cooling system for leaks.

⚠ Do not run engine longer than 10 minutes during cleaning.

⚠ Air must be expelled from cooling system when system is refilled.

1. Pressure test entire cooling system and pressure cap.
2. Slowly open filler cap to relieve pressure and allow coolant to drain faster.
3. Open engine block drain valve; drain all coolant from engine block.
4. Open radiator drain valve and drain all coolant from radiator.
5. Remove thermostats; install cover using old gasket, tighten cap screws to 47 N·m (35 lb-ft).
6. Close all drain valves after coolant has drained.
7. Fill with clean water, run engine about 10 minutes, then drain system.
8. Fill with clean water and heavy duty cleaner, drain, flush, install thermostats, add coolant.