Komatsu PC300LC-8 Operation & Maintenance Manual page 261

TROUBLES AND ACTIONS
Problem
Abnormal noise generated
(combustion or mechanical)
3 - 206
Main causes
Low-grade fuel being used
Overheating
Damage inside muffler
Excessive valve clearance
Remedy
Change to specified fuel
Refer to "Radiator coolant level
monitor lights up" as above
( Replace muffler)
( Adjust valve clearance)
OPERATION