PCV valve
Posting Guru
Joined: Aug 2002
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From: clementsport canada
PCV valve
i don't know the full reason for them, but i know that if you ever have one go bad, you'll never forget it.. truck runs like crap, screws up your timing advance, and leans your cab out... i'm a big fan of changing mine every so often now
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Joined: Dec 2001
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From: Louisville,Ky.
PCV valve
They should last about 50,000 miles, unless the engine is severly wore and has alot of blow-by past the rings.
Their purpose is to take the pressure(oil vapors and compression that gets past the piston rings) and pull them into the intake charge to be reburned in the cylinders. This keeps unwanted pressure from building up in the engine that will cause gaskets and seals to leak. This is why it is called a PCV valve. Positive Crankcase Ventilation valve.
Jimmy
Their purpose is to take the pressure(oil vapors and compression that gets past the piston rings) and pull them into the intake charge to be reburned in the cylinders. This keeps unwanted pressure from building up in the engine that will cause gaskets and seals to leak. This is why it is called a PCV valve. Positive Crankcase Ventilation valve.
Jimmy
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Joined: Jun 2001
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From: Canada
PCV valve
lxman1 - good answer - never heard it explained quite that way before. Thanks for breaking it down! PCV valves are inexpensive, so I change mine once or twice a year. Preventative maintenance is cheap.
Keep it Rubber Side Down!
Keep it Rubber Side Down!
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From: Louisville,Ky.
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Posting Legend
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PCV valve
They are cheap and they do wear out (change calibration) more quickly than you would think. They are as important as any valve in the carb for keeping your mixture correct. I change mine out annually when I winterize.
The old trick where people think "if it rattles it is still good" is not true. Check the position of the plunger on a used valve when you turn the valve over with a new valve. The used valve has had the spring fatigue from vibrating like mad and the valve pintle is now too deep in the orifice restricting flow. This causes the valve to meter the flow incorrectly. Replace them annually, or every 12-15K miles. In the OLD days we even had little tester machines that you could hook up and test the PCV operation. I wish I still had one...
Besides drawing in the bypass gasses the PCV pulls fresh air thru the engine to remove condensation etc. If the PCV intake filter is getting greasy the PCV is not drawing enuf air thru, or the engine has so much blowby that the PCV system can't keep up.
The old trick where people think "if it rattles it is still good" is not true. Check the position of the plunger on a used valve when you turn the valve over with a new valve. The used valve has had the spring fatigue from vibrating like mad and the valve pintle is now too deep in the orifice restricting flow. This causes the valve to meter the flow incorrectly. Replace them annually, or every 12-15K miles. In the OLD days we even had little tester machines that you could hook up and test the PCV operation. I wish I still had one...
Besides drawing in the bypass gasses the PCV pulls fresh air thru the engine to remove condensation etc. If the PCV intake filter is getting greasy the PCV is not drawing enuf air thru, or the engine has so much blowby that the PCV system can't keep up.
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Senior User
Joined: May 2002
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From: Garden Grove USA
PCV valve
If they go bad, they will cause all knds of havoc. It pays to spend the extra $1 and get a quality valve, since I had a no-namer not work. The result was oil being pushed out the rear main seal like crazy, and I even had oil splattering out my dipstick tube. Created a heck of a mess, and the oil dripped right onto the exhaust crating a ton of smoke...
Replaced the valve (based on recomendations here) and viola! All my oil leaks disapeared. I could not believe that the crankcase built up that much pressure on a relatively tight engine (460cid).
Change them early and often (kinda like i vote)
Replaced the valve (based on recomendations here) and viola! All my oil leaks disapeared. I could not believe that the crankcase built up that much pressure on a relatively tight engine (460cid).
Change them early and often (kinda like i vote)
Lead Driver
Joined: Feb 2000
Posts: 5,374
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From: Palm Bay, Florida
PCV valve
My recomendation would be get a factory MOTORCRAFT PCV valve, this was suggested to me because all the aftermarket ones both cheap and expensive rattle while the engine is running, and would make someone think that something else is wrong with your engine when its not, plus that annoying rapid rattleing used to drive me crazy, Ford guys have told me never use any aftermarket PCV valve in ANY Ford product,
Elder User
Joined: Feb 2005
Posts: 530
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From: in country near Boone, IA
ok guys i see this is an old thread but thought i'd ask here rather than start a new one. I understand what the PCV valve does in a normal OEM stock configuration BUT.....
what about non-stock applications..........is the PCV valve required when I have breathers installed on BOTH valve covers that will let the engine vent directly to the atmosphere?
No smog tests where I live. I am running an Eddy 4 barrel carb (650cfm, eddy Performer 400 intake) Truck is mainly a summer driver, ie. warm weather. What do you think?
what about non-stock applications..........is the PCV valve required when I have breathers installed on BOTH valve covers that will let the engine vent directly to the atmosphere?
No smog tests where I live. I am running an Eddy 4 barrel carb (650cfm, eddy Performer 400 intake) Truck is mainly a summer driver, ie. warm weather. What do you think?
More Turbo
Joined: Jun 2006
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You can run 2 breathers on the valve covers, but you will in effect have a "neutral crankcase ventilation" situation. This will result in any blow by, settling in the oil pan and contaminating the oil. This can result in early engine failure, and pre-mature ring wear. Best to run a PCV valve.
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