G424 Service Manual Adjustment and Troubleshooting174
Symptom Cause
1. Noise around the A. Rocker arm striking valve cover.
valve cover area. B. Rocker arm out of adjustment.
C. Worn rocker arm.
D. Bent push rod.
E. Collapsed lifter.
2. Noise around the A. Sticking valve.
cylinder area. B. Carbon build-up.
C. Connecting rod installed wrong.
D. Bent connecting rod.
E. Piston.
F. Piston rings.
G. Piston pin.
H. Cylinder worn.
3. Noise around camshaft A. Loss of oil pressure.
area (throughout engine). B. Valve lifters.
C. Cam bearings.
4. Noise in camshaft area A. Camshaft timing gear.
area (front of engine). B. Timing Belt.
C. Valve lifter.
D. Cam bearings.
Engine Noise
No definite rule or test will positively determine the
source of engine noise. Therefore, use the following
information only as a general guide to engine noise
diagnosis.
1. Use a timing light to determine if noise is timed
with engine rpm or one-half engine rpm. Noises
timed with engine rpm are related to crankshaft,
rods, pistons, piston pins or flywheel. Noises timed
to one-half engine rpm are valve-train related.
2. The use of a stethoscope can aid in locating a
noise source. However, because noise will travel
to other metal parts not involved in the problem,
caution must be exercised.
3. If noise is believed to be confined to one particular
cylinder, ground the spark plug leads one at a
time. If noise lessens noticeably or disappears, it is
isolated to that particular cylinder.
4. Try to isolate the noise to location in engine, front
to back, top to bottom. This can help determine
which components are at fault.
5. Sometimes noises can be caused by moving parts
coming in contact with other components.
Examples are: flywheel, crankshaft striking (pan
and pan baffle), rocker arm striking valve cover or
loose flywheel cover. In many cases, if this is
found to be the problem, a complete engine
teardown is not necessary.
6. When noise is isolated to a certain area and
component, removal and inspection will be
required. Refer to proper sections of service
manual for pertinent information.
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