a comment....

(re: '99 Boxster) Hey gang -
A few months back the car developed an embarassing rattle from the exhaust in the low RPMs. At first I thought it was the fact that all 4 of the catalytic converter heat shield bolts were gone, so I replaced those bolts. They're tight now and still it rattles.

I finally got under there with a rubber mallet and I'm pretty sure that the culprets are the heat shields just above the converters. These go all the way around the exhaust pipes and are crimped on, so there's no way they can go anywhere. They don't seem to have any bolts or clamps - they're just there and they're lose. My manual doesn't show them as a separate part from the catalytic converters - I'm guessing a weld broke?

Has anyone else faced and solved this?

Here's the heat shield I'm talking about - there's an opening under the oxygen sensor where you can see through to the exhaust pipe:

I was just replacing the cats on my car yesterday so I have the old ones right in front of me. You're right that those tube shields are not attached with any kind of bolt or clamp. They look to be bonded to the pipe at each end, and perhaps in the middle (there's an indentation), though if it's welded there's no visible sign of it on the outside. I would think that if you can identify where it's loose, some kind of tack weld spot to re-secure it (or something equivalent) would be a solution. I wonder if a metal hose clamp could also strap it down. I would think that if you can grab and wiggle the shield at each end you can figure out where it's loose.



Edited 2 time(s). Last edit at 05/20/2012 02:05PM by Trygve (Alameda, CA). (view changes)

Thanks - They wiggle around freely. I would hold one and tap with the rubber mallet and stop the noise. It's the kind of thing where if it were anywhere else, it'd be a snap to wedge something in and stop it - but not with a red-hot exhaust pipe.

Two corrections from my original post (wish I could edit):
- there are three camlock bolts on each Cat heat sheilds, not two
- When I said these loose shields were "above" the cats, what I meant was upstream of, not geometrically above.

You might check the mounts(trans & motor) on the car. I found many of the rattles or noises we had on ours went away when I replaced the afore mentioned parts.
regards