Elusive boost leak

[09subisti]

Hey guys, so for the past week or so I've been trying to find a significant boost leak after I had just bought my 09 STi, and I've tried my boost leak tester with soapy water but only found a small leak. Not the one that I'm loosing 3-4 psi out of. I cant see it, or feel it while testing.
Ive sent data logs to Cobb and they've comfirmed my problem of a large boost leak. I'm just stage 1 tuned with an AEM intake.
Last night when I was driving, I could hear the leak start after I made about 5 psi. It sounds exactly like the BPV when I shift, but it's a longer, quieter, constant "pssshhh" sound until I shift...then it gets louder for a split second. And the sounds comes on crisp, it doesn't increase gradually, I can fluctuate the sound by going back and fourth on the gas.
I can hear the turbo, and it makes a really fine whistle, but thenwhen I hit 5 pounds of boost the sound of the turbo completely changes to the loud "psshhhh".
I pulled the BPV off and the spring is good and strong, so I'm kind of baffled now, and I've ran out of things to try. Has anybody experienced this? Are there other tests I can perform other than a smoke and boost leak test? Is there a way to directly test the stock BPV?

 

[Batmobile_Engage]

You could use the starting fluid or brake cleaner method, you can even use a propane torch that isn't lit. You spray a mist around certain parts of the engine bay at idle. The engine is pulling vacuum wherever that boost leak is. The leak might pull in some of the mist and the engine will stumble or rev slightly. Some people that smoke, waft a cigarette around the engine bay and watch to see if the smoke gets pulled one way or another. It could be though, that the leak doesn't pull vacuum but only opens up under boost.

 

[09subisti]

I'm pretty sure the leak is only under boost. The car idles fine. But at this point I'll try anything haha. Thank you!

 

[Alin]

Well, hang on a minute. At what PSI(s) are you doing the boost leak tests at?

 

[Spamby]

Check all connections and hoses pre and post turbo.
The throttle body to IC coupling and the turbo to IC hose are particular problem areas. I'd replace them for good measure with nice silicon pieces and t-bolt clamps.
The turbo inlet is another disaster waiting. Check that and maybe even replace as preventative measure.

 

[09subisti]

Anywhere from 5psi-20psi max. I could hear the air coming out somewhere but I could not find it at all.

 

[Alin]

Exactly what [MENTION=1507]Spamby[/MENTION] said. :tup:

 

[09subisti]

I have checked them, but I didnt see any areas where they would be leaking from. The only spot I saw was from the turbo outlet to the inter cooler. That piece had a tiny leak, which was fixed by tightening the clamp. The sound of the air is coming from the driver side intercooler area. I sprayed the whole thing with soapy water and got nothing.

 

[09subisti]

I'll replace those later this week when I get the chance just to be sure.

 

[Alin]

Could be the y-pipe on the bottom end of the intercooler then. I had to take mine apart and seal it up in the past.

 

[HolyCrapItsFast]

Could be the y-pipe on the bottom end of the intercooler then. I had to take mine apart and seal it up in the past.

This is my initial guess to.

What BPV do you have and what PSI are you targeting?

 

[09subisti]

Il check the Y pipe gaskets today. When I took the intercooler off before to visually inspect them they looked fine, and the bolts were tight.
I have the stock BPV, and the target depends on the gear and how long the pull is. In 1st and 2nd it targets 22psi. In 3rd and 4th it targets 17.1 psi.

 

[09subisti]

hey guys, I have an update. So I checked the Y pipe gaskets and they are good.
I rigged up a way to pressurize the intercooler by itself with the BPV attached. I can't build any pressure past 8 psi or so. The BPV just spews air even if I apply that same amount of pressure to the vacuum fitting on BPV. It only gets louder when I apply vacuum instead of pressure. (Imitating a shift)
I think my BPV is bad, or it's just not sealing.
Also, when I took the BPV off a whole bunch of oil came out of the vacuum fitting on the BPV. Is this normal?

 

[Alin]

Im pretty sure oil in BPV is bad. Wait for others to confirm!

 

[09subisti]

Okay thanks. it's odd though, there is no oil whatsoever in my intercooler, makes me wonder how it go there. Smh.

 

[Spamby]

That's weird about the oil. I'd say if your BPV can't hold pressure then try to get your hands on another.

 

[09subisti]

Yeah, I'm trying to find one. It looks like my only option is to buy one from Subaru or get the Cobb adjustable one. I just don't want to spend a whole bunch for a stupid BPV.

 

[Spamby]

I used the cobb xle and it didn't work for me. It was like it wouldn't hold boost. Supposedly you could change the spring but I couldn't find different springs. Plus, the return hose was a pita to seat on the squarish vent port.
I think synapse is supposed to have a good recirc valve?

 

[Alin]

Stock BPV are only about $30-$40 on nasioc. If for some reason you can't find one, look for a used Forge BPV. :tup:

 

[Alter3go]

There should be no oil in the BPV at all. Also the stock bpv don't fail often and the only thing I can think of is you're getting 22 PSI as a target on a stage 1 tune which is a little high on stage 2 plus it doesn't even run 21 psi. I'd uninstall the AP and see if your targets r hitting stock and if you have the stock intake. You may need to look at that AP playa those do fail as well.

I also suggest looking into an AOS (I have one for sale btw lol) or catch can with that oil.

Was there oil in the IC?

I like the cobb XLE was good for me and was adjustable beside what [MENTION=1507]Spamby[/MENTION] was saying about the return hose it's a bit hard to fit, but it fits. IMO stay stock since you're only stage 1