Good points ... but I think I'm on to sumpn here. Quit pee'ing on my charcoal.Originally Posted by Scott Larson
Oh boy, here we go again...Not to start a major debate or anything but, the PCV does indeed provide positive crankcase ventilation, hence the name! Equalization of pressure is conveniently provided by the oil drainback passages in the heads and block, there are no internal valves to retain pressure in either. The oil "spluge" described coming from the dipstick tube or the PCV or the oil cap is from worn piston rings 99.999% of the time. (I did see once where a piston had been holed by too hot of plugs but how often does that happen? The oil spit out of an open oil filler neck is as Tom suspected, merely spash, not pressurized oil. Worn valves won't pressurize the crankcase as they do not have an open passage to the crankcase. They will cause a loss of compression and backfiring through the intake manifold if it is the intake valves that are worn. Worn valve seals can leak oil into the combustion chambers to be burned off during operation but even they will not pressurize the crankcase. As far as the returning oil flow being somehow pressured into blowing back through the return passages, highly unlikely as the oil return passages are far more voluminous then the pressure passages. Could it happen? Only if the return passages were so sludged-up and restricted as to cause a positive-pressure environment within the return-oil system. If that's the case, the owner of said auto has far greater things to be concerend about, namely, no oil gettin' to nothin'...
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