Join Date: Mar 2016
Location: Lake Mary, Florida
Re: Oil pan gasket blown out - pressure?
Yep...crankcase pressure. I had a 6 cylinder blow out the rear rubber oil pan gasket. The PCV valve was plugged solid, so the crankcase was unable to expel any of its pressure. Add to that, the rings were pretty bad, and most likely caused the PCV to gum up and plug over time.
If you change over from a PCV valve setup to a valve cover vented cap, you may experience oil blow by on the valve covers, depending on the health of the engine (rings, valves/valve stem gaskets). I notice that lots of folks will eliminate the PCV valve, and route the PCV valve line to a "catch can" instead, to capture the crankcase fumes and oil mist.
On newer cars that use a throttle body (fuel injection) using a "catch can method" instead of the PCV valve can rid the throttle body valve from getting oiled up, and throwing a diagnostic code.
You would only need to place a vented cap on one side of the two valve covers, but most folks, for cosmetic reasons, put one on each valve cover. The engine will "pull" fresh outside air from one side of a given valve cover, which routes eventually to the crankcase, and then the crankcase pushes out its crankcase fumes to the other valve cover. This "other side" valve cover is the valve cover that has the PCV valve, which then routed these crankcase fumes/oil mist to the carb (or newer cars, the throttle body valve), to be reburned. You would plug the carb end to prevent an air intake leak.
I recall my dads old 56 Chevy having the "down draft" tube. This tube was used in the place of a PCV valve or breather cap on a valve cover to directly route the crankcase fumes to the air. He would drive off, and spew smoke from under the car! I guess the feds got involved and made the auto manufacturers stop that, hence the PCV valve arrangement.
Never argue with an idiot; they'll only drag you down to their level, then beat you with experience.
Last edited by bucko; Oct 24th, 18 at 07:44 AM.