Blow-by occurs when the explosion that occurs in your engine’s combustion chamber causes fuel, air and moisture to be forced past the rings into the crankcase. Your engine’s rings must maintain an excellent fit in order to contain the pressure.Click to see full answer. Similarly one may ask, how do I stop my engine from Blowby? How to Reduce Engine Blowby With Oil Treatment Allow the engine to cool before performing work. Remove the ignition keys from the vehicle to ensure that the engine will not be started. Open the hood of the vehicle. Locate the engine oil filler cap and remove it. Remove the engine oil filler cap by turning it in a counterclockwise direction. Secondly, what would cause blow by in a Cummins? Excessive crankcase pressure or white smoke is a blow-by issue caused by: Fuel, air, and moisture forced past the rings into the crankcase. Similarly, it is asked, is engine blow by normal? 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 diesel blow-by can be caused by piston rings that are sticking in the bore.What is excessive Blowby?That means that the engine is producing too much blow by–that the pistons, rings, or cylinder walls are all worn out and that too much exhaust is getting into the crankcase. That means it’s time for an engine rebuild.