Well my main cat would sometimes rattle with this nasty squeaky noise. I knew it was the heat shield, but bending the shield didn't quiet it for long. Also, I sometimes noticed an exhaust leak sound especially with the pass. window down. Finally, I pulled the cat to have a look.

The stock heat shield is two layers, and the top outer shield is bolted into multiple brackets. These brackets attach to the main body of the cat inside the inner heat shield - and most of these brackets were broken from the main body but held in place by the inner shield, making a nasty squeak noise.



So first, I removed the top outer shield and pulled out all the brackets which weren't still welded solidly to the cat body. One of them had black soot on it - the exhaust leak. (Bottom one it pic above). Turns out it broke a tiny hole in the cat body as it broke loose (see below).



A trip to an exhaust repair shop fixed that in 10min and $10. He cut away the inner heat shield and welded a big blob over the leak. Leak and squeaks fixed.



Looking at the pipes of the cat, the shields on them also had some wiggle room. I had tried in the past to keep them still by wrapping a hose clamp around it to pinch it tight, but it could still wiggle. So I bent the corners of the flanges across the diagonal to put some tension in the shield where it touches the pipe. (See red lines in pic are the bend lines). Nice and solid now, they won't be rattling for quite a while.



Dave

 

did you notice any increase in boost and power once you got the cat fixed?

 

A loose heat sheild and a small hole are not going to cause any performance issues. Performance issues look like this: clogged cat pics

 

Its always nice when you can fix something yourself on these cars without dumping a load of cash. Good job.

If you have not installed the cat yet, I suggest this mod:

Have both flanges welded to the pipe on the outside. Have a bead welded all the way around, so that it seals nicely. AFTER this is done, take a grinder and grind down the inside weld to make it smooth. The inside welds reduce the 2 1/2 inch openings to just over 2 inches, which restricts flow slightly. I noticed a slight increase in performance form doing this. It wasn't big, but it was there.

 

Nice thought Adam, but the cat's back on the car.

No, performance didn't change, but the sound of squeaky cheap rice is gone.

Now, I need to find that tiny exhaust leak in the engine bay - I suspect the LIM gasket or crack in the exhaust manifold. That'll be a lot of work for a simple fix.

Dave