SHAFT 1108384 - Caterpillar

The typical crankcase blowby on a new engine is approximately 0.02 m3/bkW h (.50 ft3/bhp h).Measure the crankcase blowby of new engines. Record the data. Continue to measure the crankcase blowby. Comparing the recorded data to the new data provides information about the condition of the engine.Note: Crankcase blowby is one of the three factors that help to determine the in-frame overhaul interval. For more information, see the Operation and Maintenance Manual, "Overhaul (In-Frame)" topic in the Maintenance Section.After a new engine is used for a short time, the crankcase blowby can decrease as the piston rings are seated. The crankcase blowby will gradually increase as the following components show wear:
piston rings
cylinder linersNote: A problem with the piston rings causes the oil to deteriorate rapidly. Information regarding the condition of the piston rings can be obtained from the measurement of the crankcase blowby and the results of oil analysis.The crankcase blowby of a worn engine may exceed the crankcase blowby of a new engine by two times or more.A sudden increase in crankcase blowby could indicate a broken piston ring. The following conditions are other potential sources of crankcase blowby:
Worn valve guides
A turbocharger seal that leaksA rebuilt engine can have a high crankcase blowby due to the following factors:
The piston rings are not seated properly.
Worn parts such as valve guides were not replaced.Excessive crankcase blowby may indicate the need for an overhaul. By keeping a record of the results, a gradual increase in the amount of crankcase blowby will be noted.Use the 1U-8860 Large Engine Blowby Pickup Group to measure the blowby. Refer to Special Instruction, SEHS8984, " 1U-8860 Large Engine Blowby Pickup Group " which is provided with the tool.Record the crankcase blowby for the engine. Keep a record of the results.For more information, see the Service Manual, "Systems Operation/Testing and Adjusting". For assistance, consult your Cat dealer.