There are a number of power related problems including excessive lubricating oil consumption, smoke, blowby and
poor performance that can be caused by inadequate sealing between the piston rings and the cylinder walls. A
blowby measurement can help detect the problem.
Verification of the damaged or worn component requires visual/dimensional inspection of rings, pistons and cylinder bore.
The cause of piston ring wear can range from wear overa long period of service to a dust-out in a short period of
time because of poor maintenance of the air intake system. Refer to Section 3 for troubleshooting the Air System.
During repair it is essential that the cylinder wall be deglazed so that new rings will seat against the cylinder wall.
Failure of the rings to seat can result in high blowby and excessive oil consumption.
However, it is also critical that the cylinder walls be thoroughly cleaned after the de-glazing. Grit left in the cylinder wall will cause rapid wear out of the new rings leading to the previously discussed power problems.
Overheating of the engine from a loss of coolant will cause the cylinder to overheat resulting in seizure of the
piston. Loss of piston cooling lubricating oil can also lead to piston seizure.
Improper maintenance of the lubrication system is the primary cause of reduced main bearing life.
Normally, worn bearings can be detected by reduced oil pressure. But if this wear goes undetected, the excessive
clearance will cause the connecting rod to strike the crank shaft causing a distinct knocking sound.
A connecting rod knock occurs when the engine is not loaded. Verify by first applying load and then unloading
and listening for the knock.
