Redtop SR Boost Leak! - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

nakedave · 03-21-2012, 10:00 PM

Ok so I've been trying to trace down a pretty large vacuum/boost leak for a while. Finally got around to testing it today. First blocked off my intercooler piping, no leaks there. Reconnected the piping and ran another test. It took me a while to find it, but I'm leaking from the back left side of the head. Down below the valve cover. I can't see it, but I can hear it when I run a tube down behind that back side of the head.
I replaced the head gasket last year and used that copper sealant to help seal things up. I also used ARP studs that have been re-torgued since. The head was decked and I haven't let it overheat. Not saying it isn't my head gasket, but any other ideas what might be leaking back there? I'm going to perform a compression test and leak down test tomorrow and see what kind of results I get.

codyace · 03-21-2012, 10:04 PM

Do a leak down and compression test. You probably just hear the air rushing into the engine when testing.

cotbu · 03-22-2012, 02:22 AM

From a boost leak test you shouldn't be pressuring the crank case.....If you test like I test, it should be to see if the system holds pressure? 5psi or so then slowly leak out. Anymore than that will probably blow out the VC gasket and dipstick tube anyway.

The only things I can think of that might be leaking is IACV, intake mani and Brake booster Vacuum source. Those aren't that serious of leaks and are easy to fix.

I don't think it's the headgasket.

nakedave · 03-22-2012, 05:42 PM

Well, did compression/leak down test today. Results are not good.
Cylinder compression /leakedown results
1.111lbs, 25% leakage
2. 107lbs, 35% leakage
3. 105lbs, 30% leakage
4. 97lbs, 35% leakage
This was done on a cold motor, but still. I could hear leaking passed the rings in each cylinder.

03-21-2012, 10:00 PM	#1
nakedave Join Date: Oct 2005 Location: Lubbock, Tx Age: 42 Posts: 28 Trader Rating: (0) Feedback Score: 0 reviews	Redtop SR Boost Leak! Ok so I've been trying to trace down a pretty large vacuum/boost leak for a while. Finally got around to testing it today. First blocked off my intercooler piping, no leaks there. Reconnected the piping and ran another test. It took me a while to find it, but I'm leaking from the back left side of the head. Down below the valve cover. I can't see it, but I can hear it when I run a tube down behind that back side of the head. I replaced the head gasket last year and used that copper sealant to help seal things up. I also used ARP studs that have been re-torgued since. The head was decked and I haven't let it overheat. Not saying it isn't my head gasket, but any other ideas what might be leaking back there? I'm going to perform a compression test and leak down test tomorrow and see what kind of results I get. __________________ 92 240sx w/ SR20DET swap and manual conversion!-http://www.cardomain.com/id/slidways240

03-21-2012, 10:04 PM	#2
codyace Post Whore! Join Date: Dec 2004 Location: Poconos, PA Age: 39 Posts: 8,030 Trader Rating: (58) Feedback Score: 58 reviews	Do a leak down and compression test. You probably just hear the air rushing into the engine when testing. __________________ *Want Air Conditioning in your SR20 Swapped car? Check out www.sr20acbrackets.com for more information! Quest Alternator Conversions for SR20!* Check my Group Buy! Tired of lousy internal gates? Go external wastegate with one of my manifolds, Check out my group buy

03-22-2012, 02:22 AM	#3
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 49 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	From a boost leak test you shouldn't be pressuring the crank case.....If you test like I test, it should be to see if the system holds pressure? 5psi or so then slowly leak out. Anymore than that will probably blow out the VC gasket and dipstick tube anyway. The only things I can think of that might be leaking is IACV, intake mani and Brake booster Vacuum source. Those aren't that serious of leaks and are easy to fix. I don't think it's the headgasket. __________________ LoverTechnologies "Half Broken Things!"

03-22-2012, 05:42 PM	#4
nakedave Join Date: Oct 2005 Location: Lubbock, Tx Age: 42 Posts: 28 Trader Rating: (0) Feedback Score: 0 reviews	Well, did compression/leak down test today. Results are not good. Cylinder compression /leakedown results 1.111lbs, 25% leakage 2. 107lbs, 35% leakage 3. 105lbs, 30% leakage 4. 97lbs, 35% leakage This was done on a cold motor, but still. I could hear leaking passed the rings in each cylinder. __________________ 92 240sx w/ SR20DET swap and manual conversion!-http://www.cardomain.com/id/slidways240