Engine Noise: Inspection

SYMPTOM CHART - ENGINE NOISE

Type of sound

Condition

Possible cause

Regular clicking sound

Sound increases as engine speed increases.

Valve mechanism is defective.
Incorrect valve clearance
Worn camshaft
Broken valve spring

Heavy and dull clank

Oil pressure is low.

Worn camshaft main bearing
Worn connecting rod bearing (large end)

Oil pressure is normal.

Loosened flywheel mounting bolt
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 RPM.

Sound is reduced when fuel injector connector of noisy cylinder is disconnected. (⁽¹⁾

Worn camshaft 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 cylinder is disconnected. (⁽¹⁾

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 disconnected in turn. (⁽¹⁾

Unusually worn valve lifter
Worn cam sprocket
Worn camshaft journal bore in cylinder head

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

Valve tappet noise

Incorrect valve clearance

NOTE:

⁽¹⁾

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 OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. > after connecting the fuel injector connector.