Hi All,

I'm been trying to find the source of an extremely annoying "rattle" coming from the rear end of my car (2008 TT).

Here's a vid:

There are two separate issues but I believe they're related.
When the car is stone, dead cold, at startup it makes a godawful rattle. The rattle is not uniform and changes intensity and pitch through warm up.
Once the air injection shuts off and the idle settles in, the rattle goes away.
You can see this in the video at the 1:53 mark.
When the car is warm...even 5-6 hours after being shutoff and restarted...the startup rattle is non-existent.
I thought it was a heat shield or loose exhaust hangar..etc but we tightened everything up, double checked the heat shields and can't find anything to make that sound so I'm wondering if something else is going wrong back there.

The other sound is heard in the video around the 2:06 mark. This is a rattle/fart sound that only occurs when the engine is off idle to ~ 1.2k rpm. I've blipped the throttle to around 2k rpm so you can hear to sound off idle..then die out...then come back as the rpms drop back below 1.2k and then go away at idle. This sound is persistent whether the car is cold/warm/hot.

I do have a catless, 3" xpipe exhaust (that I love the sound of) but this sound was not present immediately after it was installed. It started happening a week or two after the install and was subtle at first but has gotten progressively louder. I'm not ruling out that there's an issue with the exhaust but after spending way to much time sniffing fumes down there...it just doesn't sound like it's coming from the actual exhaust.

Not sure if anyone has any ideas. Could it be an exhaust leak or something worse going on? The car drives great, pulls strong, and doesn't have any driveability issues whatsoever.

But that sound....

Thanks All!

Tom

 

When did the noise start? After an exhaust install? Sounds like some type of resonance at certain RPM's you can hear the bumper/something buzzing and vibrating. Have you had the bumper off recently? Intercooler ducting not rattling/rubbing on something? Loose bolt rattling inside or I think you mentioned driving it. Would have tumbled out by now :/

 

Sounds like muffler straps are a little loose or something along those lines?

 

Could be a baffle in the muffler. As it heats up it expands and tightens up. Just a guess though.

 

Hoping it's not internal to the exhaust but that's certainly a possibility. I'm going to take the bumper off again and give everything another examination. It really does sound like a loose strap or heat shield but I just haven't found it yet and since no one has said "oh yeah...that definitely sounds like your flux capacitor is going bad" I'm hoping I'll find that I just missed something simple.

 

When you have the bumper off see if the rattle continues...at least that will rule out the exhaust hitting the bumper and causing the noise

 

I'm with Rix.

The exhaust system of a stock Turbo is a pretty snug fitting assembly with not much spare room between things. Any change to the exhaust system is just an opportunity for introducing a rattle, or buzz, or other noise.

That's exhaust system related. An exhaust hanger connection is loose, broken, there's something loose in the exhaust, or possibly a heat shield is loose or touching something.

Time to sniff some more exhaust fumes.

 

Are there heat shields on the car? Could be loose.

 

My oem exhaust had crazy annoying rattle, turned out to be the heatshields. Swapped for a Kline no more rattle for me, and great engine sound instead

 

Take the bumper off, start the car while it's rattling and start grabbing stuff. You'll figure out where it is pretty quick when whatever you grab stops the rattle. Wear some gloves, things get hot quick .

 

I think it's exhaust related 100%

 

Did you ever figure this issue out ? I have a similar noise and I'm leaning towards motor mounts. Thanks

 

Yes! It ended up being the water pump in my case.
The impeller shaft had worn and caused things in the pump to start making physical contact with one another causing that rattle. It was all chewed up inside. New pump and noise went away.

 

Thanks so much! Makes sense for my issue. Mine also is irregular at cold starts like yours. I'll check it out.

 

Here's the noise from mine. It's quite similar to yours goes on for about a minute and a half when cold and then disappears. I've started hearing it also low speeds when warm and driving. Is this what you experienced? Here's my video. Thanks