Chevy 454 PCV valve question

1985air345 · 03-01-2003, 12:36 PM

Brett enlightened me that PCV stands for Positive Crankcase Ventilation and he changes his when he changes his air filter. I have not changed mine yet.

Please educate me some more.
What would be the symptoms of a bad PCV valve? Should I change it along with the air filter?

(FYI - I'm going to change mine this week)

59toaster · 03-01-2003, 01:06 PM

Well it is a spring loaded valve that once there is some vacuum applied that it will open and suck blow by gasses and water vapor out of the crank case. Those gasses are then fed into the engine and burned.

Some of the symptoms that a problem with the PCV would create is idle problem, poppin up the dipstick. It may also cause the oil to blacken up a little faster if they are stuck closed since the crud that would other wise be air born condences and gets back into the oil.

I replace mine about every 9K (every third oil change). Typically if the rattle when you shake them they are usualy ok but as cheap as they are...replace it. An engine with high miles may have more blow by and require a more frequent change interval.

There will be a second filter in the air cleaner where the crank case will get the freash air that should also be changed regurlarly as well. It will be into the side of the air cleaner assembly and have a pipe down into the valve cover oposite of the PCV.

The rubber gromit that those fit in on the valve cover tend to get hard. If yours is like that most parts stores have them in the "Help" isle for a couple bucks.

wb13798 · 03-01-2003, 07:10 PM

i dont change mine i clean it out with some carberator cleaner. if it has a metalic sound when i shake it i put it back . if it has a dull sound i pitch it and get a new one . not often that i pitch one. the other filter i was cleaning them out with deisel fuel , dont have a deisel unit around any more so i replace when i gets dirty and gumed up. about once a year.
the spring of the year i replace all filters and dump and change the mobil 1 in the motor and i flush my transmission. with three gallons of new transmission fluid. little bit of over kill but i want new fluid in the xmission. and grease the chassis. that works for me . lol
al

87MH · 03-01-2003, 08:07 PM

If pressure builds up in the crankcase it could conceivably cause the oil not to flow through the labyrinths properly.

The crankcase also requires a partial vacuum to pull off the acidic water vapors that boil out of the oil, and these are then recycled through the cylinders and out the exhaust.

A malfunctioning PCV valve would hinder the removal of these acids.

The PCV's are really cheap and easy to get to. If there is any question of the age or nternal condition, change it out.

NASCAR345 · 03-01-2003, 10:48 PM

1985air345,
Everyone's comment are right. If you don't know where it, it is located on the top of the driver's side valve cover. there is a hose connecting it to the base of the carb or to a fitting on the intake. I recommend you pull it out and take it with you to the parts store to ensure you get the right one. Check the grommet it mounts into for cracks or see if it is hard. If, replace it too. It will help keep oil film building up on the valve cover. You'll spend more time getting the cover off and reinstalling than the task itself. If you break the plastic elbow off in the hose simply use some needle nose pliers. Break it in half by squeezing on the ouside of the hose and pull the pieces out. if the hose is hard an brittle too, go ahead and replace it. This will prevent any vacuum leaks causing poor running and performance of the engine.

Hope this helps,
NASCAR345