Abnormal Noise - Xinchai 490B Series Manual

6.7 Abnormal noise

Cause of trouble
Too big injection advancing angle
resulting in rhythmic metallic
knocking sound
Nozzle dripping or seized needle
Too big valve clearance resulting
in clear rhythmic knocking sound
Piston and valve impinging
resulting in rumbling even
rhythmic knocking sound. When
your finger lightly touches screws
on top of cylinder head cover a
beat of piston impinging can be felt
Piston and cylinder head impinging
resulting in powerful knocking
Broken valve spring, bent push
rod or worn tappet resulting in
light knocking sound from valve
mechanism
Sound resulting from too big
clearance between piston and
cylinder liner. Its intensity will
decrease as the engine warms up
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Remedies
valve
Re-adjust injection timing
Clean, repair or change needle valve
Adjust valve clearance
Increase valve clearance, decrease
connecting rod bearing, clearance or change
connecting rod bushing
Replace with the thicker cylinder head gasket
Change faulty parts and re-adjust valve
clearance
Change piston or cylinder line