Exhaust sound from oil fill cap (crankcase).
I have been a heavy equipment mechanic for over 20 years so I am no stranger to
diagnostics. That said, I am trying to figure out this exhaust noise and extreme blowby I
noticed from the oil fill on the head. The car does have 166,000 pampered miles but runs
great. Compression is approx. 175 psi on all four. I does not smoke or burn oil. Could
there be a problem with the EGR valve? No codes... ever. Thanks
Here is an answer that was posted a few years back to your question: Most engines now days employ an oil return/check valve in the pan that pressurizes the block, including the rocker/cam(app) cover area, and is normal. If you remove the filler cap, engine running, it will do exactly what you describe. If there was that much blow-by, there would be a CEL(app), fouled plugs, and pcv or O2 (app) issues all over the place. Even if there was blow-by, and the pcv valve was bad, removing the oil filler cap, engine off, would instantly relieve the pressure and you would see a lot of oil vapor. That's all. -----
should not be excessive blow-by at the oil filler tube, should be very little ( enging running and oil filler cap off ) if there is excessive blow by then it has to be the piston rings, were more then likely installed improperly, note: the gaps in the rings has to be staggered on the piston , course one would first check the PCV ( positive crankcase ventilation ) valve ..if it rattles when you shake back and forth then it;s okay..otherwise replace it.
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