Re: Vacuum lesson please
PCV is an acronym for Positive Crankcase Ventilation. It was designed to work best when combined with an air cleaner breather. There should be a PCV valve located in a grommet in the drivers side valve cover with a vacuum line that runs to manifold vacuum. The valve allows a limited amount of manifold vacuum to suck or pull crankcase vapors out of the engine and then the get burned along with the incoming air/fuel mixture as the engine is running.
There should be another rubber grommet in the passenger side valve cover with a larger diameter hole than the PCV valve grommet that a breather cap plugs into. The breather cap should have a hose that runs from itself up to a nipple on the underside of the air cleaner. This breather allows the passenger side of the engine to have additional crankcase ventilation when necessary and/or fresh air to be pulled in to replace what the PCV valve sucks or pulls out of the crankcase.
Depending on the condition of the cylinders, pistons and rings, some engines will have more or less blow by. More blow by means more crankcase ventilation is going to be necessary. At idle, the breather may be allowing fresh air flow into the crankcase but at higher rpm's when more blow by is occurring, the breather actually allows the crankcase pressure that can't make it out the PCV valve to be pulled into the engine through the breather and then be burned with the air/fuel mixture.
The PCV system replaced the old down draft tube systems of earlier engines that were "less friendly" to the environment as they just released all the crankcase gases (and quite often oil) into the atmosphere and onto the ground. You'll always have some amount of blow by in any engine (the less the better) and thus an engine needs a way for the crankcase to vent or the engine crankcase pressure will create a way at the weakest link which will usually be one or more gaskets weeping, leaking or out right blowing.
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