Excessive Crankcase Pressure or Excessive White Smoke When Removing Oil Fill Cap


This is a blow-by issue caused by:

Cause: Fuel, air, and moisture forced past the rings into the crankcase, or contaminated and diluted oil in the crankcase

Solution: Use Stiction Eliminator and Diesel Extreme to free up both sides of piston rings. If the piston rings are worn out, they will need to be replaced.


Some blow-by is normal on any diesel engine. This is because the combustion pressure is just too great for the piston rings to hold completely.

Excessive blow-by can be caused by piston rings that are sticking in the bore. One of the ways to check if blow-by is too great is to put your oil filler cap upside down on the filler hole. If the cap gets blown off, there is too much pressure in the crankcase.

Blow-by can be caused by piston rings that are worn out. A cylinder with worn out rings will have low compression and will likely cause a misfire. These piston rings need to be replaced.

If you have any questions, feel free to contact one of our diesel experts.


Blow-By - Heavy-Duty Cummins Symptoms
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