Dakota 2WD V6-3.9L VIN X (1997)
Hydraulic Tappet: Testing and Inspection
Noise Diagnosis
1. To determine source of tappet noise, operate engine at idle with cylinder head covers removed.
2. Feel each valve spring or rocker arm to detect noisy tappet. The noisy tappet will cause the affected spring and/or rocker arm to vibrate or feel rough
in operation.
NOTE: Worn valve guides or cocked springs are sometimes mistaken for noisy tappets. 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.
3. Valve tappet noise ranges from light noise to a heavy click. A light noise is usually caused by excessive leak-down around the unit plunger, or by the
plunger partially sticking in the tappet body cylinder. The tappet should be replaced. A heavy click is caused by a tappet check valve not seating, or
by foreign particles wedged between the plunger and the tappet body. This will cause 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, tappet assembly should be removed
for inspection and cleaning.
4. The valve train generates a noise very much like a light tappet noise during normal operation. Care must be taken to ensure that tappets are making
the noise. If more than one tappet seems to be noisy, it's probably not the tappets.
