Possible Exhaust Leak At Full Boost?

[Subaru_Nation555]

(Wasn't sure whether to post here or in the exhaust section)

When I boost past 5 psi or so I get a "whooshing" sound from what I thought was the cabin (sounds like it's coming from the floor). So I unhooked my boost gauge but the sound persisted. I checked all the vacuum lines and everything looks fine. I'm waiting for the car to cool down to check the exhaust system but would an exhaust leak only show itself at higher boost levels? It sounds fine at idle and light acceleration. Any thoughts or suggestions on what to check? Thanks for your time.

[Subaru_Nation555]

Well it seams that when I replaced the hose from the brake booster to the intake manifold I didn't sure the correct part, the OEM one feels like there is some type of valve in there. Any idea what the part number is so I can order a new one?

[PhilSine]

An exhaust leak will show itself at all levels of operation and be most noticable at acceleration of any kind. Crawl under the car with it running and listen and feel around the gasket areas for leaks. Once in awhile the pipe itself cracks (especially if its a thin walled header) and you'll have to run your hand around the pipe and feel for blowing exhaust.

[Subaru_Nation555]

Figured out it was this. Replaced it and there seems to be some sort of valve on the OEM one. Any ideas on a replacement?





http://farm4.static.flickr.com/3273/276 ... c1a6_o.jpg

[Legacy777]

Yes there is a check valve in that brake booster line. It is supposed to be there, and is there to keep vacuum on the booster to provide brake assist, and to not allow boost into the booster.

Hopefully the booster just vented the boost and no harm....but I'd keep an eye on things just to make sure.

Also, you can't buy just the check valve, you have to buy the hose.

[Subaru_Nation555]

Josh, thanks for the reply. Yeah I felt kinda silly after I realized but what are you going to do. I'll be sure to keep a close eye on it. Any idea where I can find the hose/valve assembly?

[Legacy777]

You can order it through the dealer, or I'd suggest trying to find a used one either on here, or a junkyard.

[BXSS]

+1 with the check valves keeping boost out of your Vac. assisted brakes.

I've have purchased check valves from autozone in the past before (old cars have an external check valve on the brake booster hose), but the easiest thing to do would be to get another one of the brake booster hoses from a Subaru in your local U-Pull-it.

[skid542]

Sacha, God bless you. I've had a boost leak since I installed my TMIC that's been driving me crazy to find. I replaced that hose for clearance issues and assumed the check valve was within the booster, not in the hose. Feel like a real dunce now. Consequently everytime the boost gets over 6-7 psi I hear it spewing air. I'll be going up to Autozone today to find a check valve.

FWIW, I've been running it this way for about three months and haven't had any issues in the braking dept. that I've noticed. Pedal feels a little soft but I believe that's because of the fluid - will do a full flush this weekend.

Thanks.

[BXSS]

I'd just go to the u-pull-it, as you will find a Subaru with the hose you need & might find something interesting - I found a SS in my u-pull-it JY once, but someone pulled & purchased the motor ($76 any 4 cyl) before I got there...