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Old 11-01-2018, 12:34 PM   #1
Stock-GTI
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Who has had a cracked downpipe?

What would be the symptoms of a cracked downpipe? I've heard of a few people having Cobb downpipes crack on them at the flange.

Currently my car performs well. However whenever I get into boost, there is very loud noise that comes from under the car. I can tell it's a turbo noise, just sounds like air/exhaust is escaping somewhere it shouldn't. It's not a turbo squeal or failure noise. Most audible at part throttle, partial spool.

Aside from the noise my LTFTs are consistently in the .93-.95 range at speed no crazy variances, it's just off. However they often return to .98-1.00 at lower speeds and idle. STFTs seem mostly normal.

If I'd have to guess, I'd say I have a crack at my downpipe flange right before the upper o2 causing the disparity in fuel trims. Downpipe is wrapped flange to catalytic converter so I have to drop it to check.

Or I have a crack somewhere on my exhaust manifold, but I think that's unlikely. Had the turbo dropped and gasket changed as well as broken studs fixed.

Downpipe is most likely coming off next week. Bracket rubber is cracked all the way through so I'm using it as an excuse to drop my downpipe. Also changing from dv+ to turbosmart em vr1.

Thoughts? Anything else this could be? Charge system has been checked countless times... it's not a boost leak whistle.

Who has had a cracked downpipe?
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Old 11-01-2018, 12:43 PM   #2
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I had my 42dd crack/deteriorate on me. It was making very strange sounds under boost and the car performed like shit. It threw a CEL, can't remember which one. Booked an appointment with my shop. On the lift, the dp was almost totally disconnected from the turbo. I ordered an APR dp right then and there. This happened maybe 2 years ago.
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Old 11-01-2018, 01:50 PM   #3
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Sounds like you're having the exact same symptoms I was...loud air escaping noise at part throttle. One day the noise got much worse so I got the car up on the lift. Pulled back the heat wrap to find this. I think the wrap held water and contributed to rust at the welds. No more wrap for me.

IMG_20180728_171226 by Tony G, on Flickr
IMG_20180808_224215 by Tony G, on Flickr


All fixed now
IMG_20180808_223619 by Tony G, on Flickr
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Old 11-01-2018, 03:29 PM   #4
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I had an AWE downpipe crack clean off at the flange. Massive loss of power, massive increase in noise.
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Old 11-01-2018, 03:55 PM   #5
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so moral of the story is don't wrap your dp?
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Old 11-01-2018, 04:26 PM   #6
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Quote:
Originally Posted by demon342 View Post
so moral of the story is don't wrap your dp?
Wrap your willy but not your downpipe.
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Old 11-01-2018, 05:42 PM   #7
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Quote:
Originally Posted by Tony48 View Post
Sounds like you're having the exact same symptoms I was...loud air escaping noise at part throttle. One day the noise got much worse so I got the car up on the lift. Pulled back the heat wrap to find this. I think the wrap held water and contributed to rust at the welds. No more wrap for me.

IMG_20180728_171226 by Tony G, on Flickr
IMG_20180808_224215 by Tony G, on Flickr


All fixed now
IMG_20180808_223619 by Tony G, on Flickr
Damn!

I was advised to never wrap over the cat. If it is a case of a crack under the wrap, I'm definitely not gonna re-wrap it. Don't know how much performance difference it'll make... Been trying to squeeze everything out of this setup.
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Old 11-01-2018, 05:52 PM   #8
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You can always get it ceramic coated, but that's a bit of money, but will not cause premature failure due to moisture.
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Old 11-01-2018, 06:08 PM   #9
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Quote:
Originally Posted by tdream1 View Post
I had my 42dd crack/deteriorate on me. It was making very strange sounds under boost and the car performed like shit. It threw a CEL, can't remember which one. Booked an appointment with my shop. On the lift, the dp was almost totally disconnected from the turbo. I ordered an APR dp right then and there. This happened maybe 2 years ago.
Quote:
Originally Posted by drval85 View Post
I had an AWE downpipe crack clean off at the flange. Massive loss of power, massive increase in noise.
I don't have a notable loss of power. I wouldn't know though, noise has been present for the last 7-8 revisions of my tune. The more boost the worse it's gotten. So I'm guessing some performance will gained upon fixing and tweaking the tune.

Shop tech said its just "intake resonance", almost laughed... Car sounds like a extremely pissed off tea kettle at 9-10 psi+. But since no CELs they wrote it off.

Noise is getting unbearable.
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Old 11-01-2018, 06:36 PM   #10
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You can always get it ceramic coated, but that's a bit of money, but will not cause premature failure due to moisture.
I'm guessing my powerflex bushings accelerated whatever crack it is. I'm daily driving their track bushes (90 or 95a forget which) control arm and inserts iirc noise developed around the time I installed them. I'm in Texas moisture really isn't a issue, but it's possible.

I don't know if there is a shop local to me that'll coat it. I'll look into it, wish more companies would offer it from the onset.
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Old 11-02-2018, 03:59 PM   #11
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Your noise could also be caused by a broken exhaust manifold stud. For some reason it's common on our cars for the left-most stud to snap. You'll be able to tell if you look at the manifold to block connection and see some black soot.
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Old 11-02-2018, 04:26 PM   #12
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Quote:
Originally Posted by Tony48 View Post
Your noise could also be caused by a broken exhaust manifold stud. For some reason it's common on our cars for the left-most stud to snap. You'll be able to tell if you look at the manifold to block connection and see some black soot.
Would you happen to have a pic of this? Left-most stud from what vantage point? I.e. - left driver side?
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Old 11-02-2018, 04:41 PM   #13
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Quote:
Originally Posted by Tony48 View Post
Your noise could also be caused by a broken exhaust manifold stud. For some reason it's common on our cars for the left-most stud to snap. You'll be able to tell if you look at the manifold to block connection and see some black soot.
Had this addressed in August. Shop said they found 3 broken studs, so they replaced all(5) of them. Solved a hissing noise, but the current noise persisted, actually seemed worse.... Well more concentrated.

Only other thing I can think of is that leak compromised the exhaust manifold edge and it's not sealing flush with gasket.

Really hoping it's the downpipe, simple fix vs dropping the turbo again... That was $$$.

I do plan on panning a mirror around the exhaust manifold once I have the DP off.

But I'd think I'd have bigger problems if it was the exhaust mani... I'm pushing 23-24 psi through a ported stocker lol. I would have expected it to break entirely already.

If it's the manifold I'll probably just buy a IE K04 in January.
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Old 11-02-2018, 04:50 PM   #14
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Would you happen to have a pic of this? Left-most stud from what vantage point? I.e. - left driver side?
It's the furthest to the left (lhd). Likes to snap off in the block.
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