Contour Enthusiasts Group Archives Forums General Troubleshooting What does PCV actually do?

If you don't replace the PCV valve, could it cause harm to the CAT converter? I still have the original PCV at 151K and I had both pre-cats replaced at 131K. I wonder if the 2 are related somehow?

The PCV (positive crankcase ventalation) valve's job is to do exactly that. It maintains a constant air flow through the engine crankcase. This air flow helps purge out flamable vapors in the crankcase that come from air/fuel mixture that gets past the rings during compresion, as well as the vapors emmited by the oil while it is at operating temperature. The positive airflow also carries away combustion blow by which reduces the rate of oil contamination extending the life of the oil.

The PCV valve offers little performance gains, however, the slight low presure it maintains in the crankcase can proportionally increases the pressure differential across the piston rings which helps them improve their seal.

Before the days of PCV valves, the engine's crankcase "breather" was vented to the outside air. The mixture of un-burnt fuel, combustion blow by and oil vapors makes for a nasty concoction which is toxic and harmful to your health. The PCV valve and associated plumbing takes this mixture and pipes it back into the induction system where it is sucked in a burned with the fuel inside the engine.

Yeah, what he said...except he didn't explicitly state that it can be very bad for you engine if you don't change the valve. Essentially, sludge will build up in the engine and you are getting unnecessary wear inside of the engine, thus reducing its life.

where is this located, is it easy to change?

Originally posted by JSmith:

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.. the slight low presure it maintains in the crankcase can proportionally increases the pressure differential across the piston rings which helps them improve their seal...

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Perhaps you could blow-that-by me again, since it does not compute.
PCV valve lowers crankcase pressure compared with old breather type due to vacuum of induction system.

Contour98SVT:
Under throttle body on v6.
Dealer will replace at n/c at 60K, except here and CA.

Thanx for the explanation. Dealer said that the only thing that a PCV valve would do to an engine is increase oil consumption. I've only added about 4 quarts since I've had it. Car doesn't burn any oil presently and it's on the original valve. Gas mileage is slightly down, but I am driving a lot more in the city so that's only normal. Engine still feels and sounds strong after 151K miles.

would it make sense to pipe the gasses into the exhaust allowing for more clean ain in the combustion cycle. Knowing this will cause higher emissions though.