CUTTER GP 1757546 - Caterpillar

Note: For a new G3400 Engine, the typical range for crankcase blow-by is approximately 22 to 37 L/Bkw-hr (0.6 to 1.0 cu ft/Bhp-hr).Measure the crankcase blow-by of new engines. Record the data. Continue to measure the blow-by periodically. Comparing the recorded data to the new data provides information about the condition of the engine.Note: Crankcase blow-by is one of the three factors that help to determine the major overhaul interval. For more information, see this Operation and Maintenance Manual, "Overhaul (Major)" topic (Maintenance Section).After a new engine is used for a short time, the blow-by can decrease as the piston rings are seated. The blow-by 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 blow-by and the results of oil analysis.The blow-by of a worn engine may exceed the blow-by of a new engine by two times or more.A sudden increase in blow-by could indicate a broken piston ring. The following conditions are other potential sources of blowby:
Worn valve guides
A turbocharger seal that leaksA rebuilt engine can have a high blow-by due to the following factors:
The piston rings are not seated properly.
Worn parts such as valve guides were not replaced.Excessive blow-by may indicate the need for an overhaul. By keeping a record of the results, a gradual increase in the amount of the blow-by will be noted until the amount has become excessive.To measure the blow-by, use the 8T-2700 Blowby/Air Flow Indicator. Refer to Special Instruction, SEHS8712, "Using the 8T-2700 Blowby/Airflow Indicator Group". The instruction is provided with the tool.Keep a record of the results.For more information, see the Service Manual, "Systems Operation/Testing and Adjusting". For assistance, consult your Cat dealer.