Soarin Posted June 7, 2015 Share Posted June 7, 2015 I can hear this now and then and I hope I'm not going crazy or are just over sensitive to it. When I pull into my garage and shut off my car I can hear a hiss dissipate and end. It's not very loud and I have to listen for it. I've checked all of the vacuum lines and just about everywhere air flows for cracks, leaks, and any issues and can't find any. No fluids leaking either. Everything runs superb and my car is very happy. No CEL or lights going off. Power and mileage are quite good. I had a shop replace the turbo inlet with a new OEM one, replace a few vacuum lines, and double and triple check everything. I'm also running a GrimmSpeed TMIC, stock BPV, and everything is clamped nice and tight. What could this be? The shop specializes in Subaru and says it could be extra boost at the end of the run cycle and is normal. Is that really a thing? Could the giant compared to stock TMIC be a factor? Could the BPV be leaking or worn out? If so I was looking at a Turbosmart recirculating one already. I've looked everywhere and can't find any info other than the A/C system doing a thing like this. Of which, that needs to be recharged and will be handled this coming weekend. Link to comment Share on other sites More sharing options...
apexi Posted June 7, 2015 Share Posted June 7, 2015 I agree with what the Subaru shop said. My guess is it's normal and nothing to worry about. When you shut off the car, the throttle body plate closes, even though there is still intake air going towards the throttle body. So the hissing you're hearing is that extra air going through the bypass valve, since the throttle body plate closed. I'm pretty sure that this is somewhat common on turbocharged cars, I think I heard that sound on my old eclipse gsx. *One more thing after re-reading your post. To me that doesn't mean the bpv is leaking or bad, it's just doing its job. I guess it's possible it could be leaking boost, but that symptom your describe wouldn't lead me to think that it is leaking. Link to comment Share on other sites More sharing options...
Soarin Posted June 7, 2015 Author Share Posted June 7, 2015 Thank you for the reply and the assurance. That's what I'm also coming to since everything is running as great as it is plus the shop told me that directly. I kept thinking of that, but decided to ask anyways. I tend to get paranoid about every noise after I had a bad suspension install. Though, I'm looking at BPVs just cause and am very interested in the Go Fast Bits Mach 2 TMS Recirculating one. Hahaha, I wish my wallet was fuller. Link to comment Share on other sites More sharing options...
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