Driving without pcv valve

What would happen if you drove without a pcv valve? Short term and long term?

It would act like a big vacuum leak, throw a check engine light and run poorly. Might cause damage. Might not. Why risk it for a $10 part?


Offhand, it’s hard to come up with a car part as cheap as a PCV valve.

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Fuzzy dice or pine tree air freshener maybe


Okay… good point.
I should have stated that it’s hard to come up with a functional car part as cheap as a PCV valve.

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valve stem. LOL sorry


Valve stem just cost me $83… with a TPMS sensor attached :wink:


You could plug off the vacuum line to the PCV valve, run a hose from the pcv port on the valve cover down toward the ground, to function as a road draft tube.
You’ll make your motor oil as well as the environment dirtier.
Why go back to 1962?

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The valve prevents an intake backfire from igniting the crankcase. If you have the hose, you need the valve. The system removes water vapor from the oil too. There was an open tube draining onto the road in the old days.

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… and the stench from many of those cars, when sitting behind them at traffic lights, was truly offensive. Is the OP yearning for the days prior to 1963, when PCV valves were mandated, or is he balking at spending a few bucks for a new PCV valve?

Maybe I don’t know better but if you plugged the end that goes to the intake and just left the other end open you would be spewing fumes and pollution with little effect on engine performance. Thinking my earlier cars the hose went to a filter in the air filter assembly.

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Don’t see why you couldn’t plug the vacuum hose going to the PCV valve and vent the crank case like the pre 60s cars except it would produce more air pollution. Seems like it would prevent carbon build up on the intake valves on direct injection engines.

Assuming you did it properly, (e.g: plug off the vacuum line and create a road draft tube for the pcv port), then you’d see no short term difference. It has no effect on engine performance or fuel mileage.

However, it’s the longer term that is more concerning. Without a functioning PCV valve, moisture will accumulate in the crankcase. That will reduce the life of your engine oil and will accelerate the formation of damaging sludge.

Depending on where you live, disconnecting the PCV may be illegal, for environmental reasons. It is illegal in the USA.

I’m curious about your motivation for doing this. I agree that some PCV valves are a big pain to access. But other than that, there is little to no downside for maintaining a functioning PCV.

Why go to the effort to plug the PCV tube when replacing the valve is relatively easy and inexpensive?

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My father’s '63 Plymouth had a PCV system. Whether that became mandatory in '63–or perhaps in '62–I don’t recall.

The last car I owned without a PCV valve was a 1962 Falcon. It had the vent pipe that extended down near the oil pan.

Yeah, I’m pretty sure that the 1963 model year was when PCVs were mandated in The US.

Probably not.

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The “PCV system” for my 1964 Dodge slant-6 engine was a crankcase breather cap on the valve cover, with a hose routed to the air filter housing.

As the engine got old, the piston ring blow-by grew worse and caused the engine air filter to get soaked with oil.

I replaced that hose with a homemade road draft tube and drove for years without a problem.

That was in an era when one would often see cars on the road that burned oil and produced lots of tailpipe smoke. I’m glad we see little of that with today’s engines.

Around 1991 had an old Oldsmobile (mid-60’s) that I bought for $175. It burned oil like crazy, despite the straight 40 weight oil I put in it. The PCV/breather system was simply overwhelmed, but somehow the spark plugs never fouled out. My answer was to buy a 25’ roll of 3/4 heater hose and run the “new” breather tube down along the frame and ended it next to the tailpipe, keeping all that blowby away from the passenger compartment. I used it as my drivearound junker for 2 years, then gave it to my ex-girlfriend who used it to commute 60 miles a day for another year and then sold it for $250.