Grand Caravan V6-3.8L (2009)
Lifter / Lash Adjuster: Testing and Inspection
HYDRAULIC LIFTERS
HYDRAULIC LIFTERS DIAGNOSIS - PRELIMINARY STEP
Before disassembling any part of the engine to correct lifter noise, check the engine oil pressure. See: Engine Lubrication/Engine Oil Pressure/Testing
and Inspection
Check engine oil level. The oil level in the pan should never be above the MAX mark on dipstick, or below the MIN mark. Either of these two
conditions could cause noisy lifters.
OIL LEVEL TOO HIGH
If oil level is above the MAX mark on dipstick, it is possible for the connecting rods to dip into the oil while engine is running and create foaming. Foam
in oil pan would be fed to the hydraulic lifters by the oil pump causing them to become soft and allow valves to seat noisily.
OIL LEVEL TOO LOW
Low oil level may allow pump to take in air which when fed to the lifters it causes them to become soft and allows valves to seat noisily. Any leaks on
intake side of pump, through which air can be drawn, will create the same lifter noise. Check the lubrication system from the intake strainer to the oil
pump cover, including the relief valve retainer cap. When lifter noise is due to aeration, it may be intermittent or constant, and usually more than one
lifter will be noisy. When oil level and leaks have been corrected, the engine should be operated at fast idle to allow all of the air inside of the lifters to
be bled out.
VALVE TRAIN NOISE
To determine source of valve train noise, operate engine at idle with cylinder head covers removed and listen for source of the noise.
NOTE: Worn valve guides or cocked springs are sometimes mistaken for noisy lifters. If such is the case, noise may be dampened by applying
side thrust on the valve spring. If noise is not appreciably reduced, it can be assumed the noise is in the tappet. Inspect the rocker arm
push rod sockets and push rod ends for wear.
Valve lifter noise ranges from light noise to a heavy click. A light noise is usually caused by excessive leak-down around the unit plunger which will
necessitate replacing the lifter, or by the plunger partially sticking in the lifter body cylinder. A heavy click is caused either by a lifter check valve not
seating, or by foreign particles becoming wedged between the plunger and the lifter body causing the plunger to stick in the down position. This heavy
click will be accompanied by excessive clearance between the valve stem and rocker arm as valve closes. In either case, lifter assembly should be
removed for inspection.
