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#1 |
Registered User
Join Date: Nov 2014
Location: Virginia Beach, Virginia
Posts: 83
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PCV Valve Vacuum Leak
I bought a 1978 C20 292 I6 4-spd manual new in January, 1978, and I still use it.
Often, since new, when the motor is hot it shakes horribly at idle. The problem is that the PCV valve ball sometimes does not get sucked up tight which causes a vacuum leak and the shake. There is plenty of vacuum. Plugging the end of the PCV valve with my finger fixes the vacuum leak to demonstrate what is wrong. Removing the valve from the cover and turning it sideways drops the ball into place to make it work also, and it stays in place when reinserted into its hole. Replacing the PCV valve fixes nothing. Buying cheap or not so cheap ones also makes no difference. Besides being annoying, the shaking loosens the connection to the exhaust pipe which makes that joint leak. There are probably millions of these cheap little valves in service, so they must actually work. Does anyone how I can fix this? Thanks. |
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#2 |
Registered User
Join Date: Dec 2014
Location: Northern California
Posts: 422
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Re: PCV Valve Vacuum Leak
GM had an issue with oil consumption on some of the 5.3s in trucks. The solution was a fixed orifice to replace the PCV. Not sure if 4.8 and 5.3 used the same valve number, but might be worth a shot.
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#3 |
Post Whore
![]() Join Date: Aug 2014
Location: Sacramento, CA
Posts: 10,826
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Re: PCV Valve Vacuum Leak
plug the port on the carb, stick an aftermarket breather in the valve cover, every couple months wipe off the valve cover
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#4 |
Registered User
Join Date: Jul 2011
Location: WV
Posts: 946
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Re: PCV Valve Vacuum Leak
Many different solutions. Here's mine. Use the PC valve thats in the valve cover as an elbow and put another inline.
__________________
72 GMC C2500 402/Th400 first truck (still have) 77 GMC C3500 CC dually Sold ![]() 70 C50 dump truck "Rusty" 87 K10 Suburban Sold 93 K2500 xcab 6.5TD 96 GMC K2500 Suburban 6.5 TD |
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#5 |
Registered User
Join Date: Nov 2014
Location: Virginia Beach, Virginia
Posts: 83
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Re: PCV Valve Vacuum Leak
I like the #4 answer. Do you have a recommendation on what to ask for at my FLAPS?
Thanks |
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#6 |
Registered User
Join Date: Jul 2011
Location: WV
Posts: 946
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Re: PCV Valve Vacuum Leak
First is a 70's Buick with a 231 V6. They have 2 hose barb ends but one is larger than the other. That might work for you.
__________________
72 GMC C2500 402/Th400 first truck (still have) 77 GMC C3500 CC dually Sold ![]() 70 C50 dump truck "Rusty" 87 K10 Suburban Sold 93 K2500 xcab 6.5TD 96 GMC K2500 Suburban 6.5 TD |
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