Needing some help finding a vacuum leak

[Pizzarolls4]

sorry if this has already been mentioned but there is a check valve where the PCV routes back into the intake. is your check valve in backwards? maybe you dont have a check valve, I only know what is there for a turbo engine.

 

[Goblinfanclub1234]

the LNF has a PCV in the manifold plus additional check valves in the vacuum hoses.

 

[Rauq]

LSJ only has that check valve in the IM and the hose from the valve cover port that's supposed to go to the intake tube.

Have you tried capping the intake at the filter and smoke testing the intake system? I'm not sure if you'll get enough flow past the throttle body to get smoke out of a potential IM leak though.

 

[Pizzarolls4]

So I believe I have it fixed kind of odd but I pulled the IM again and blew through the pcv valve there seemed to be a difference in how much air was passing through the brand new one and the crusty old one installed the old one and the problem is gone

 

[Pizzarolls4]

Thanks everyone for the ideas/suggestions.

 

[Gtstorey]

Now the question is was the new bad or is the old one not functioning. My LSA supercharged LS3 has a pretty good whistle of air through the PCV lines and is normal.

 

[Pizzarolls4]

Thats a good question I'm not really sure how to check that it's functioning correctly other than blowing through it lol but when the donor was running the noise wasn't there obviously because old pcv valve was in it. I've heard of people deleting the stock pcv system maybe in the future I'll look into that.

 

[escapepilot]

Does the PVC valve act as a one way valve under boost? Could the new one have been letting boosted air flow back into the valve cover? If it is indeed a one way valve, that could be tested.

 

[Pizzarolls4]

Does the PVC valve act as a one way valve under boost? Could the new one have been letting boosted air flow back into the valve cover? If it is indeed a one way valve, that could be tested.

I think this build has been a learning experience along the way when u blow into the top of it which is the part that mates with the hole in the head air comes out the bottom if u blow through the bottom no air comes out the top.

 

[Desert Sasqwatch]

Boost pressure must be blocked from blowing into the crankcase, but intake manifold vacuum must be able to pull air from the crankcase when the engine is not in boost. Is this what you are describing?

 

[escapepilot]

It does sound like the valve is functioning properly. Strange that swapping in the old one made a difference then. But if it's working now, send it.

 

[Ross]

Do you know the manufacturer of the PCV valve that didn't work? Do you have picture of it? It would be nice to document it, so other builders can avoid this issue.

 

[Pizzarolls4]

This is what I used matches the part number same as the saab part number on saabusa.com they were having some website issue only reason I bought it off Amazon but same part I put in my daily driven lsj and never had an issue. The part on my daily was installed pre-covid so maybe part quality is just garbage now lol

 

[Pizzarolls4]

I think this is the one I pulled from my daily a couple years ago part number is different on top believe its oem part and the saab one has the 55557180 stamped on top.

 

[Pizzarolls4]

Boost pressure must be blocked from blowing into the crankcase, but intake manifold vacuum must be able to pull air from the crankcase when the engine is not in boost. Is this what you are describing?

Can u explain differently don't really understand what you're meaning.

 

[Dale E]

Post # 73 is a PCV for the Supercharged Cobalt. This one was discontinued some time ago. I gave Lonny a box with a couple of each in it about 2 years ago, but I don't know if he still has them.

Genuine Saab 9-3 2003-2011Positive Crankcase Ventilation Valve PCV 55557180 | eBay

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Post # 74 is the PCV for a Turbo Cobalt.

For Chevy Cobalt 2008-2010 ACDelco GM Original Equipment PCV Valve 808709036616 | eBay

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