dgeesaman

iTrader: (7)

Stock intake, cat, muffler, Pettit DP.

I just finished the hose job and the car now sounds more raspy - the exhaust note isn't loud, but it isn't as deep as it was before. Kinda like a crappy ricer. In the engine bay you can hear it.

I've taken apart the UIM and intake elbow a couple times and looked for loose pieces, thinking that was the cause. Would not replacing the gaskets cause this? Would a very small exhaust leak sound with way without the telltale loudness of an exhaust problem?

Dave

(just tired of sounding like an old Accord w/ 3" muffler)

dgeesaman

iTrader: (7)

bump

I don't do all this maintenance to have it sound like crap

Sonny

Sounds like you have an exhaust leak, man. Check the dp/cat joint and also the cat/catback joint. Small leaks can be easily seen by blowing smoke over the area in question....very easy to do if you're a smoker.

Sonny

dgeesaman

iTrader: (7)

Thanks. I will try that, but using something other than a cigarette.

Dave

dgeesaman

iTrader: (7)

1) Does a squirt of ATF harm your main cat?
2) Could a leak on the intake piping have a similar sound?

BigIslandSevens

iTrader: (4)

I had a LIM gasket leak a few times and that sounded like chitty chitty bang bang( if your old enough to know what that is) Or a popcorn maker.

Also the exhaust gaskets sound similar, and since you have a DP on I would try and retorque the nuts on the DP to turbo. and check for a exhaust leak there.

dgeesaman

iTrader: (7)

Done that during the hose job last month, which is why I'm a little baffled. I loosened all four bolts so I could put some anti-seize on them and retightened all of them evenly. I did not tighten in a crisscross pattern though, but I doubt that alone would do it.

The sound is clearly coming from the engine bay area, so I might go for a new TB/UIM gasket and UIM gasket to start. Maybe also new turbo inlet gaskets.

Dave

WaLieN

What would be the result of blowing smoke on an exhaust leak? Would the smoke blow back or something?

Toadman

You can use a squirt bottle with soapy water. Look for bubbles.

dgeesaman

iTrader: (7)

Someone recommended using a copper-based high-temp gasket sealant as an alternative to replacing the turbo-dp gasket. He says you can scrape it off if needed, so I might try it.

Anyone tried this stuff? To save $75 for a little mess doesn't sound bad to me.

Dave

dgeesaman

iTrader: (7)

Well, I pulled the downpipe today. Down at the cat-dp connection, there is visible black soot indicating a small leak.

In addition, the downpipe gasket had white powder residue on the faces, and since the powder went from the inside edge to the outside edge, indicates another leak. This would explain the noise and odor I got from that part of the engine bay. It was very hard to pinpoint at idle, but when driving around 4k under load it was a lot louder.

I'm going to put on new gaskets at each end, replace a screwy looking stud on the cat flange, and check all flanges with a straightedge. I will try to post pics tomorrow.

Anyone got new gaskets they can sell me? Last I heard, dealer price for the pair is approaching $90

dgeesaman

iTrader: (7)

Cause: exhaust leak at the downpipe-manifold connection.

Finally, the resolution:

I had been using some high strength socket head cap screws instead of the stock studs. Turns out they were too long. I think they were 30mm, I cut them to 25mm. Some tediously slow dremel cutting later, when I tightened it down it sealed well. I also swapped out my very flattened gasket for a new one, but I think the real fix was the bolts bottoming out.

Dave

M104-AMG

iTrader: (8)

Dave- when you had this leak, did it sound like you could hear the slapping of the rotary seals ?

It's driving me nuts, although I have a perfect 10-8-10 pattern. . . .

:-( neil

dgeesaman

iTrader: (7)

No, I couldn't hear anything like that - just a bees-in-a-can sound that is less than impressive.

FWIW, I ended up fixing this leaky exhaust issue by thoroughly flattening each flange face with a big metal file. I had to re-face the downpipe at both ends, the main cat at both ends, and the muffler. While I did have some persistent leakage at the DP gasket, most of the leakage was b/t the cat and dp - once I got clean metal-metal contact, I could use regular gaskets without issue. Before that I always needed some high-temp RTV to fill the gaps in the seal, and it was burning out.

Dave