Ear Piercing Squeal - HELP!
I'm working on diagnosing the PCV system right now. Taking off the oil cap or popping the PCV valve out of the block while the engine is running relieves a strong vacuum inside the block. I understand that the PCV valve is supposed to vent excess positive pressure from the block back into the intake, but if it's pulling a vacuum at this location, I'm not convinced that the PCV valve itself is bad. Any idea why such a strong vacuum is being generated?
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Joined: Dec 2010
Posts: 2,610
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From: Maricopa, AZ
GM PCV Valve Part Number: 25179136
I'm working on diagnosing the PCV system right now. Taking off the oil cap or popping the PCV valve out of the block while the engine is running relieves a strong vacuum inside the block. I understand that the PCV valve is supposed to vent excess positive pressure from the block back into the intake, but if it's pulling a vacuum at this location, I'm not convinced that the PCV valve itself is bad. Any idea why such a strong vacuum is being generated?
I'm working on diagnosing the PCV system right now. Taking off the oil cap or popping the PCV valve out of the block while the engine is running relieves a strong vacuum inside the block. I understand that the PCV valve is supposed to vent excess positive pressure from the block back into the intake, but if it's pulling a vacuum at this location, I'm not convinced that the PCV valve itself is bad. Any idea why such a strong vacuum is being generated?
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
If you remove the oil cap, put your hand over it, then rev the engine, does the vacuum get stronger or weaker? If it gets stronger, pull the valve covers and look for an intake valve that isn't opening. Just a theory.
Last edited by hrcslam; May 13, 2014 at 05:33 PM.
So....now I feel like an idiot.
I had my right valve cover venting to my intake manifold instead of my throttle body. Although they're only about 2" apart, the manifold vacuum port pulls very hard vacuum and the throttle body port is nearly atmospheric. With the setup I had, my intake manifold was sucking a large volume of air out from my valve cover and was dumping it back into the intake manifold.
Looks like my problem is now solved and hopefully this thread will help others down the road. You've gotta be careful with those vacuum lines, folks!
Big shout out to hrcslam for his help in diagnosing this, I owe you a beer next time I'm in Arizona!
I had my right valve cover venting to my intake manifold instead of my throttle body. Although they're only about 2" apart, the manifold vacuum port pulls very hard vacuum and the throttle body port is nearly atmospheric. With the setup I had, my intake manifold was sucking a large volume of air out from my valve cover and was dumping it back into the intake manifold.
Looks like my problem is now solved and hopefully this thread will help others down the road. You've gotta be careful with those vacuum lines, folks!
Big shout out to hrcslam for his help in diagnosing this, I owe you a beer next time I'm in Arizona!
Last edited by BrownBoy; May 20, 2014 at 09:42 PM.
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
So....now I feel like an idiot.
I had my right valve cover venting to my intake manifold instead of my throttle body. Although they're only about 2" apart, the manifold vacuum port pulls very hard vacuum and the throttle body port is nearly atmospheric. With the setup I had, my intake manifold was sucking a large volume of air out from my valve cover and was dumping it back into the intake manifold.
Looks like my problem is now solved and hopefully this thread will help others down the road. You've gotta be careful with those vacuum lines, folks!
Big shout out to hrcslam for his help in diagnosing this, I owe you a beer next time I'm in Arizona!
I had my right valve cover venting to my intake manifold instead of my throttle body. Although they're only about 2" apart, the manifold vacuum port pulls very hard vacuum and the throttle body port is nearly atmospheric. With the setup I had, my intake manifold was sucking a large volume of air out from my valve cover and was dumping it back into the intake manifold.
Looks like my problem is now solved and hopefully this thread will help others down the road. You've gotta be careful with those vacuum lines, folks!
Big shout out to hrcslam for his help in diagnosing this, I owe you a beer next time I'm in Arizona!
