ME(H6DO)-90
Engine Noise
MECHANICAL
29.Engine Noise
A: INSPECTION
(NOTE*)
When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory.
Therefore, carry out the clear memory mode and inspection
mode after connecting the fuel injector connector.
Ty p e o f s o u n d C o n d i t i o n P o s s i b l e c a u s e
Regular clicking soundSound increases as engine
speed increases.
•Valve mechanism is defective.
•Incorrect valve clearance
•Worn valve rocker
•Worn camshaft
•Broken valve spring
•Trouble of tappet
Heavy and dull clankOil pressure is low.•Worn camshaft main bearing
•Worn connecting rod bearing (large end)
Oil pressure is normal. Damaged engine mounting
High-pitched clank
Sound is noticeable when
accelerating with an overload
condition.
•Ignition timing advanced
•Accumulation of carbon inside combustion chamber
•Wrong spark plug
•Improper gasoline
Clank when engine speed is
between 1,000 and 2,000
rpms.
Sound is reduced when fuel
injector connector of noisy cyl-
inder is disconnected.
(NOTE*)
•Worn crankshaft main bearing
•Worn bearing at crankshaft end of connecting rod
Knocking sound when engine
is operating under idling speed
and engine is warm
Sound is reduced when fuel
injector connector of noisy cyl-
inder is disconnected.
(NOTE*)
•Worn cylinder liner and piston ring
•Broken or stuck piston ring
•Worn piston pin and hole at piston end of connecting rod
Sound is not reduced if each
fuel injector connector is dis-
connected in turn. (NOTE*)
•Unusually worn valve lifter
•Worn cam gear
•Worn camshaft journal bore in crankcase
Squeaky sound — • Insufficient generator lubrication
Rubbing sound — • Poor contact of generator brush and rotor
Gear scream when starting
engine—•Defective ignition starter switch
•Worn gear and starter pinion
Sound like polishing glass with
a dry cloth—•Loose drive belt
•Defective water pump shaft
Hissing sound —•Insufficient compression
•Air leakage in air intake system, hose, connection or manifold
Timing belt noise —•Loose timing belt
•Belt contacting with case/adjacent part
Va l ve t a p p e t n o i s e —•Incorrect valve clearance
•Trouble of tappet
