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View Full Version : What is causing my loud exhaust whistle, whoosh, under heavy load.



bigrobby
11-09-2012, 08:49 PM
99 a4 1.8t apr 94 octane.....205k miles.

my exhast system is completely stock except for there is no muffler....resonator back is straight pipe (welded, no leaks at weld). been that way for a while.... been chipped for 100k miles.
but under high load it makes a loud whooshing or whistling noise. it's getting worse. it's not the turbo....i know what that sounds like. it's not the flange that connects turbo to cat....i've blown that off twice...welded it last time to where it will never come off again.

it sounds like an exhaust leak whistle. pressure escaping from a small gap. but it's loud. i checked for leaks and found some....like the joint that connects the exhaust about halfway down the car. fixed that....smoke test doesn't show any others. but smoke test doesnt put much pressure on it. i can't get the noise to happen on the lift.....need a lot more load to make the noise happen.

I'm thinking the flex pipe or resonator. i ran it with open exhaust after flex.....didn't hear the noise really....but exhaust was so loud that i'm not sure i would've heard it. besides....no pressure built up in flex pipe area since it was open after.

maybe the resonator is breaking apart or something and causing a whistle.....but i swear it sounds like exhaust gases escaping at the wrong place.....sounds like it's from the rear of the car but i can't be sure...have to be accelerating hard.

it's been months of chasing a phantom exhaust leak.....and now i don't even know if that's even causing my loud whooshing noise. i will find this damn noise.......but if someone knows what i'm talking about....i wouldn't mind a little help. thank you.

zerokiller698
11-10-2012, 06:23 AM
sure its an exhaust sound?
It might be a boost leak

xdewaynex
11-10-2012, 07:20 AM
I ran without a muffler for a bit (car had a fart can on it, when I got it) while I waited on my Vibrant muffler. I had somewhat of the same sound, and figured it was the exhaust hitting the rear valence and kind of being split by it. Sounds weird, but thats all I could come up with.

bigrobby
11-10-2012, 08:25 AM
yeah it's not a boost leak. it's coming from underneath the car somewhere. also, it's more dependent on load than boost. it will make the noise at 3500 rpm, 15 psi, but also 6000 rpm at 8 psi.

it's strangely inconsistent too. sometimes it's more of a whooshing sound...like a large amount of air escaping...and sometimes it's like a loud whistle.

bigrobby
11-10-2012, 08:27 AM
I ran without a muffler for a bit (car had a fart can on it, when I got it) while I waited on my Vibrant muffler. I had somewhat of the same sound, and figured it was the exhaust hitting the rear valence and kind of being split by it. Sounds weird, but thats all I could come up with.

makes sense but i do have pipes coming out of the back and past the rear valence. also, the noise wasn't there when i first got rid of the muffle. factory resonator is still on there.

seanj130
11-10-2012, 08:37 AM
Did you ever think that your CAT was clogged and that is why you blew apart where the turbo connects to the cat...

bigrobby
11-10-2012, 08:46 AM
Did you ever think that your CAT was clogged and that is why you blew apart where the turbo connects to the cat...

i can't promise my cat is perfectly healthy with this many miles, but i've welded that flange shut after i blew if off twice. it's never coming off again. I have thought about debris from the cat or something else going downstream and causing issues but i don't know. the noise comes from under the car, not under the hood. sounds like it's coming from the rear but i'm not counting out the flex pipe. also should note this is a southern car, no rust anywhere.

also, it runs damn good at 205k miles if the cat is clogged. but it's still something i'm considering.

love the quote in your signature by the way.

bigrobby
11-10-2012, 05:36 PM
ok so today i'm getting somewhere. found a different flange cracked. this time it's a the intermediate? pipe.......where it connects to the downpipe. directly above the right front inner cv joint. pretty decent crack....i'll weld it monday but this has to be the stupid noise. i've checked everything else. my brother's car (same car) is starting to make the same noise. i'll be checking that same spot

bigrobby
11-13-2012, 09:14 PM
got it welded up. noise is still there. the flex pipe is really all that's left

seanj130
11-13-2012, 10:02 PM
Ok big rob.. Why do you think that the flange has blown off twice? there is something that is not allowing pressure out.