Pcv screams!!

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TexasDart

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Trying to figure out why and how to stop the PCV valve from screaming. When it's cold it makes a high pitch noise. When it warms up it doesn't scream anymore. I figured it was the old mechanical PCV valve, so I went and bought a new plastic style...found a grommet..seal good. STILL SCREAMS...:) What would cause this. I can pull the vacuum line and plug up the hose and scream goes away.

Any suggestions would be greatly appreciated.
 
TexasDart said:
Trying to figure out why and how to stop the PCV valve from screaming. When it's cold it makes a high pitch noise. When it warms up it doesn't scream anymore. I figured it was the old mechanical PCV valve, so I went and bought a new plastic style...found a grommet..seal good. STILL SCREAMS...:) What would cause this. I can pull the vacuum line and plug up the hose and scream goes away.

Any suggestions would be greatly appreciated.
Click to expand...

Does it scream when it's out of the valve cover? Since you changed it, it makes me wonder if it is something else. Try it cold with the valve just laying out. It may be sucking air from some other point that swells up and stops after it gets warm.
 
Are you sure the screaming comes from the PCV valve or is the pressure escaping out another orfice? If you pull the valve while it is screaming maybe you are just relieving the pressure. Maybe something other than the valve is clogged upstream in the hose to the carb/intake.
 
Just for giggles,replace the PCV hose.My guess,somone used non oil reistant fuel line.The oil penetrates and seperstes the layers in the line.It breaks down,and the hose collapses.Lack of airflow finds the spot and relieves the psi.My guess,that might be it.
 
is there some thing in the valve cover blocking the air flow ?? like the baffel to close to the pcv
 
are you sure your not getting your PCV mixed up with the supercharger?? :D

cuz its supposed to do that!
 
I'm on board with the hose collapsing or maybe a problem with the breather?

Either that or there is something really scary under the valve cover and it wants the hell out of there.
 
I'm running a 32/36 Weber on this one and I've got it plumbed into the base of the carb it doesn't go into the air cleaner...mabye that's a problem.

I have the old style Metal PCV on there so it shouldn't be too close to the baffle.

I haven't tried leaving it hooked up with the PCV valve just laying out.

I'll check the hose. I've got some extra hose laying around.

Probably should spray some carb cleaner around to double check for leaks.
 
Valve hose to the carb base and breather to the air cleaner is correct on stock 1 & 2 barrel carbs. Do check/ replace hose and make sure the carb's hose nipple is not blocked. I recall that years ago I discovered a lot of oily black junk had over time collected. Now I rebuild my 1 barrel at least every 2 years.
 
TexasDart said:
I haven't tried leaving it hooked up with the PCV valve just laying out.
Click to expand...

This would be a quick and easy check to see if it's in the hose, carb gasket etc, or further down the line. Start it with the valve out and put your finger over the valve and see if it "screams".
 
My oil cap doesn't have a hose to the air cleaner. It's just an aftermarket oil cap with no capability to stick a hose on it to route it to the air cleaner...does it need this? Do I need a different style of oil cap so that I can route a hose to the air cleaner?
 
As I said in my first post. There is something that is leaking and when it warms up it swells and quits. Things expand when they get warm.

The first thing you need to do is determine is where it's at, by process of elimination and isolation.
 
I think that the breather to air cleaner hose is a smog control idea to re-cycle fumes down the carb for burning. OK idea - otherwise; out the breather -through the firewall or hood into the vents and cab. But is ok for engine and I do not think has an effect on pcv.

I did see that there is two pcv in the shop manual. one has a H on a flat end with a black washer = most applications. The valve for the 170 has a 6 stamped on the end with a white washer. Might be some thing to check out!
 
You do have an open breather cap in the valve cover, correct? Otherwise you're going to pull a pretty good vacuum in the crankcase and any air trying to get in might whistle ....I'm thinking dip stick/tube area or oil fill cap or maybe valve cover gasket acting like a reed. If that isn't the problem, I'd check the vacuum reading in the intake to see what differences there are between cold and hot. There may be a leak that seals itself when hot. Carb gasket maybe?
 
Sorry guys...I swear I'll look at it...probably be Wednesday before I get a chance though.

Thanks for all the suggestions.
 
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