Subaru LEGACY 2006 Manual page 823

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MECHANICAL
28.Engine Noise
A: INSPECTION
Type of sound
Regular clicking sound
Heavy and dull clank
High-pitched clank (Spark
knock)
Clank when engine speed is
1,000 to 2,000 rpm
Knocking sound when engine
is operating under idling speed
and engine is warm
Squeaky sound
Rubbing sound
Gear scream when starting
engine
Sound like polishing glass with
a dry cloth
Hissing sound
Timing belt noise
Valve noise
NOTE*)
When disconnecting the fuel injector connector, the malfunction indicator light illuminates and DTC is stored in ECM memory.
Therefore, perform the Clear Memory Mode <Ref. to EN(H4SO)(diag)-43, OPERATION, Clear Memory Mode.> and Inspection
Mode <Ref. to EN(H4SO)(diag)-34, PROCEDURE, Inspection Mode.> after connecting the fuel injector connector.
Engine Noise
Condition
• Valve mechanism is defective.
• Incorrect valve clearance
Sound increases as engine
• Worn valve rocker
speed increases.
• Worn camshaft
• Broken valve spring
• Worn camshaft main bearing
Oil pressure is low.
• Worn connecting rod bearing (large end)
Oil pressure is normal. Damaged engine mounting
• Ignition timing advanced
Sound is noticeable when
• Accumulation of carbon inside combustion chamber
accelerating with an overload
• Wrong spark plug
condition.
• Improper gasoline
Sound is reduced when fuel • Worn camshaft main bearing
injector connector of noisy cyl- • Worn bearing at crankshaft end of connecting rod
inder is disconnected.
(NOTE*)
Sound is reduced when fuel • Worn cylinder liner and piston ring
injector connector of noisy cyl- • Broken or stuck piston ring
inder is disconnected. • Worn piston pin and hole at piston end of connecting rod
(NOTE*)
Sound is not reduced if each • Worn cam sprocket
fuel injector connector is dis- • Worn camshaft journal bore in cylinder head assembly
connected in turn. (NOTE*)
— Insufficient generator lubrication
— Poor contact of generator brush and rotor
• Defective ignition starter switch
—
• Worn gear and starter pinion
• Loose drive belt
—
• Defective water pump shaft
• Insufficient compression
—
• Air leakage in air intake system, hose, connection or manifold
• Loose timing belt
—
• Belt contacting with case/adjacent part
— Incorrect valve clearance
ME(H4SO)-94
Possible cause