Aerostar 2WD V6-245 4.0L (1990)
Timing Chain: Fundamentals and Basics
TIMING CHAIN REPLACEMENT HINTS AND TIPS
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Always replace both the timing chain and both sprockets as a combined unit.
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A worn timing chain will not properly fit the teeth of a new sprocket and will result in a premature failure.
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A new timing chain will rapidly wear away the teeth of an old sprocket.
NOTE: Since the water pump and drive belts will need to be removed during this procedure, it is important to note any related deficiencies prior
to starting the procedure.
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Inspect the water pump for signs of leakage and inspect the pulley for any looseness or wobble. If any wobble is detected the water pump
should be replaced.
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Inspect the drive belts and replace if necessary.
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Inspect the drive belt idler/tensioner pulleys for looseness and wobble. Replace any pulley which does not spin freely or has any wobble.
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Inspect the cooling fan clutch for proper operation.
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Under cold conditions the clutch should be disengaged, allowing the fan to spin freely.
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Under hot conditions the clutch should tighten up, coupling the fan to the water pump pulley/shaft.
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Rotate the engine to number 1 Top Dead Center prior to removing the timing chain.
NOTE: The alignment marks on the camshaft and crankshaft gears are positioned at number 1 Top Dead Center.
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When removing the water pump, any bolts which show signs of corrosion should be replaced and the holes/threads should be chased or re-tapped.
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Oil pan removal is required to remove the timing cover. Bolts from the oil pan extend through the bottom of the timing cover. Removing the bolts
and loosening the remaining pan bolts to remove the timing cover will tend to cause oil leakage from the pan gasket.
NOTE: To prevent leakage, when the oil pan is removed or the bolts are loosened, the gasket should always be replaced.
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When tightening the oil pan bolts always use a torque wrench. Correct sealing requires the gasket to be evenly torqued across its entire sealing
surface.
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Do not turn the crankshaft or camshaft with the pulleys off. Using slip joint pliers or pipe wrenches to turn the crankshaft will damage the surface
and affect the press fit of the pulley.
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Silicone sealant should be used very sparingly. Excessive sealant which squeezes out on the inside of the gasket can accumulate and restrict the oil
pump pickup screen or the coolant heater core.
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Inspect the chain guides and tensioner foot and replace if excessively worn.
NOTE: If the chain guides are worn past 50% of their original thickness the guides may not last the life of the new chain and should be replaced.
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When installing the chain leave the initial slack on the tensioner side, the opposite side should be tight. If any slack is left on the side opposite of
the tensioner, upon initially rotating the engine the camshaft/crankshaft alignment will be incorrect.
