Hiss/whistle On High Boost: Exhaust Or Boost Leak?

[V28VX37]

Hi all,

I was recently cruising down a country road and hit a pothole and/or some loose debris at its edge. Massive bang. I had a quick look under the car straight after and there seems to be a fresh scrape under the mid muffler but no other damage that I could see. The exhaust is hanging low so it's likely to have taken a hit, and if not it must have been the intercooler. The cooler and piping looks fine from the outside, too.

The car runs fine but seems to have developed an occasional hiss/whistle noise on high boost and might have lost a bit of power, hard to tell though. It still generates boost well enough. I pulled out the airbox and tightened all IC piping clamps underneath but this didn't make a difference.

Any ideas on what else to check?

Looking at some other threads I wonder if any of these might be the cause:

• boost leak (loose clamp, cracked cooler?)
• exhaust leak (manifold, gasket, broken stud/s etc.?)
• slightly damaged turbo?

And yeah the car's an R34 GTT auto with a front mount (Trust vertical flow), stock turbo, turbo back exhaust and a recent Nistune running ~11psi.

[Room42]

Hi all,

I was recently cruising down a country road and hit a pothole and/or some loose debris at its edge. Massive bang. I had a quick look under the car straight after and there seems to be a fresh scrape under the mid muffler but no other damage that I could see. The exhaust is hanging low so it's likely to have taken a hit, and if not it must have been the intercooler. The cooler and piping looks fine from the outside, too.

The car runs fine but seems to have developed an occasional hiss/whistle noise on high boost and might have lost a bit of power, hard to tell though. It still generates boost well enough. I pulled out the airbox and tightened all IC piping clamps underneath but this didn't make a difference.

Any ideas on what else to check?

Looking at some other threads I wonder if any of these might be the cause:

• boost leak (loose clamp, cracked cooler?)
• exhaust leak (manifold, gasket, broken stud/s etc.?)
• slightly damaged turbo?

And yeah the car's an R34 GTT auto with a front mount (Trust vertical flow), stock turbo, turbo back exhaust and a recent Nistune running ~11psi.

Sounds obvious but get under the car and look for the dented parts. Then you can see what was affected. Then you can examine the affected parts and find the hole/crack/bent pipe/culprit.

[V28VX37]

Sounds obvious but get under the car and look for the dented parts. Then you can see what was affected. Then you can examine the affected parts and find the hole/crack/bent pipe/culprit.

Good call, I gotta get in on a hoist somewhere and have a proper look.

[Room42]

Car ramps are pretty cheap these days. Reverse it up on a set and get out the torch if necessary. Nothing like lying on the ground under your car. I've benchpressed many a box in. Fun

[MADE]

I had the same problem recently after encountering an obstacle in the road similar to you. It turned out to be the gasket between the turbine and manifold.

[V28VX37]

I had the same problem recently after encountering an obstacle in the road similar to you. It turned out to be the gasket between the turbine and manifold.

Thanks mate, good to know it's not a completely isolated event. Did you replace the gasket yourself or get a shop to do it? How much, if you don't mind me asking?

I should call the bloody council or something, what a PITA when they don't keep the roads in check...

[MADE]

I got the entire turbine gasket kit, but the gasket that was bad cost under 20USD. Pretty easy to change, so I did it myself but I thought the GT2535 was a direct swap and excluding the lines and inlet it is. Now Im waiting on those parts since I figured I'd save tim by swappin now. If you DIY it should be less than 3 hours for a first timer. You gotta pull it apart anyway Id suggest going with the turbine gasket kit,. Worst it could be is a broken exhuast stud which I have replaced on a previous RB also.

Check all your flanges also, working backward to the turbine. Also if one of your gaskets are shot your gonna more of an exhuast sound from the engine or area affected.

Edited October 8, 2011 by MADE

[V28VX37]

Check all your flanges also, working backward to the turbine. Also if one of your gaskets are shot your gonna more of an exhuast sound from the engine or area affected.

Thanks, I'll have a look at these areas. Fingers crossed it's just a gasket and not one of the flanges or studs...

[boostn0199]

Do you have a return style cooler? When this happened to me my returning pipe on the cooler hit something and it ripped the silicon joiner on the cooler so check them if you have one.

[V28VX37]

Do you have a return style cooler? When this happened to me my returning pipe on the cooler hit something and it ripped the silicon joiner on the cooler so check them if you have one.

Thanks, yes I do, although it's a Trust turnflow (vertical flow) rather than the more common horizontal flow type (e.g. Blitz, Cooling Pro). Still worth checking though, just need to get the car on a hoist.

[V28VX37]

Ok I had the workshop look at the car. They can hear the hiss/whistle too but couldn't locate the cause (it's very momentary).

It doesn't seem to affect performance at all either, they even chucked the car on the dyno and it runs the same numbers as before.

Weird.

I might leave it for now, or perhaps do this boost leak test if I cbf.

[MADE]

IME if you have a torn coupler it's going to be more than just annoying to drive.

[Godzilla34]

Hi, I just had the same problem. Hissing at High boost. It was just the bolts from the exhaust flange were loose which was easily repaired just replacing with lock nuts and a new gasket.

[V28VX37]

IME if you have a torn coupler it's going to be more than just annoying to drive.

The manifold to turbo flange/gasket/nuts all look fine on the top and both sides (better than in the photo you posted). Can't really see underneath. Car drives fine.

I'll see if I can tighten the nuts though.

[V28VX37]

Well I'll be damned, looks like it's all sorted.

I tightened (just a touch) the three accessible manifold to turbo nuts (top ones & bottom right), top right seemed the least tight.

I also tightened four of the turbo-dump bolts, one of the top ones was a touch loose.

The hiss/whistle is now gone.

Big thanks to MADE, Godzilla34 and others for your suggestions!

Reading through some other posts it sounds like bolts/nuts coming loose can be an issue with aftermarket front/dump pipes that put more stress on the turbo and manifold. I might look at replacing a section of the front pipe (JJR bellmouth) with some flex pipe later on to relieve this a bit, especially as I keep on scraping the exhaust on a weekly basis pretty much...