Hello all,
Thanks for the good comebacks on Positive Crankcase Ventilation System
operation. Just a few more things we should all remember.
1) Enclosed crankcases have always needed ventillation due to vaporized
oil, combustion gasses leaking past piston rings (blowby), etc. It
all has to go somewhere.
2) The old way was to run a tube downward from the crankcase, with the
end cut off at an angle (road draft tube). Car motion was supposed
to create some suction (vacuum) here and draw out the fumes. In
turn, fresh air was supposed to be drawn into the crankcase through
the filter in the oil filler cap. This really did not work very
well. It also caused considerable air pollution.
3) Beginning in the early 60s it was realized that pollution could be
reduced by using intake manifold vacuum to suck the fumes out of the
crankcase-Presto-along came PCV. It was realized that more than
just pipes and hoses were needed-Presto, the PCV valve. It is the
only control in the system and does all 3 things we have brought up.
in our postings.
4) Interestingly enough it soon became apparent that PCV also
appreciably reduced sludge deposits inside the engine and helped
keep the oil cleaner. So it has become far more than just an
emission control device.
Cheers,
Dave Kernberger
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