my heat shields rattled

There is a pronounced rattling noise during low rpms when driving in 1st and 2nd gear. I have tried to look underneath the car, but nothing seems loose, the exhaust seems fine. What could this noise be?

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bigmach
There is a pronounced rattling noise during low rpms when driving in 1st and 2nd gear. I have tried to look underneath the car, but nothing seems loose, the exhaust seems fine. What could this noise be?

A little more information might help.

What rpm do you mean by low rpm?

Steady state driving, accelerating or coasting down?

Does it ever happen in any other gear?

Edited 1 time(s). Last edit at 09/20/2011 07:51AM by bigmach. (view changes)

When the engine is idling at neutral standing still, there's no rattle. When I give some gas, it starts to rattle, maybe around 1500-3000 rpms. This happens when standing still and when in first or second gears at normal 1500-3000 rpm driving. Sounds like something is loose in either the muffler/cats

There are two over the rear cats and two inline on the exhaust pipe forward of the cats. Generally there is nothing you can see when they are loose.

Mine did that and drove me crazy finding it . It turned out to be the 2 nuts that hold the mufler up behind the rear bumper they had somehow gotten slightly loose when i found them tightened the heck out of them and no more rattle

The noise seems to be coming from the muffler/cats. Went to a local shop who told me my cats might be gone. How can I make sure it's the cats before replacing these expensive cats?

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bigmach
The noise seems to be coming from the muffler/cats. Went to a local shop who told me my cats might be gone. How can I make sure it's the cats before replacing these expensive cats?

I think the most likely cause would be what boxterra or poorsche1 said. Loose heat shield or loose muffler.

Went to an independent mechanic. How easy is it to fix it (DIY) if either the heat shield or muffler is loose?

10 minutes tops.

Generally, it is pretty easy to tell if the cats are starting to go(breaking apart internally, rattling around in canister). Put the car up in the air, and start it when it is cold, get under the car, the sound or rattle is pretty evident. For some reason, there were a few years to these cars where Porsche sourced some poor quality exhaust parts. If your secondaries are starting to go, you might be able to install bypass pipes as an option(depending on state, year, etc..). We had a fair bit of exhaust rattles, and I found the drive train mounts were the majority of the issue.
regards

i could hear them when i pounded the exhaust with my fist.
i had a very difficult time replacing them with the car on the ground. not enough clearance. with the car on a lift it would be as easy as undoing and redoing the fasteners (they aren't plain old screws.)

--
MY 2000 S, Ocean Blue, Metropol Blue, Savanah Beige.
Bought June 2000 - Sold May 2010

So it turns out it was a loose heat shield, took it out and the rattling is gone!