Heat Shield Removal

[Dr Jay]

I have been chasing down this noise in my exhaust system for a few years. The noise is hard to explain, but if you have ever heard the rattle from an old exhaust shield vibration before it lets go, that's what it sounds like. The rattle only shows up under hard acceleration about 4 or 5 thousand rpm and it stops within 2 seconds of hearing it. I'm running the mrt catted h pipe and I'm wondering if anyone has run into issues with cat shields vibrating like this, even when the spot welds look good?

Like I say, the noise has been there for a few summers, the catback and headers have been replaced so the midpipe is the only consistent piece with the noise. I'm thinking of cutting the shields off the cats, will they come right off after drilling the spot welds? Will I have to worry about heat if I do remove them?

 

[RedDaemon]

its very UNlikely that it is this but as a precaution, i would check your spark plugs too

 

[Dr Jay]

Excellent point you make. I had a different exhaust noise last year that sounded like a leak that ended up being a loose plug. I check the plugs twice a year now and I have ruled it out this time.

 

[RedDaemon]

Pypes seems to be able to get away with not having heat shields; is MRT really all that different in these terms

ya know..it could also be the crap inside the cats too, i think thats my problem (havent heard it recently tho )

 

[Dr Jay]

I believe the cats on the MRT are high flow Magnaflows. I never though about anything inside the cats, can you tell if you take the pipe off and shake it? The cats don't have many miles on them so I wouldn't think there should be any issues but I have seen stranger things happen.

 

[RedDaemon]

I believe the cats on the MRT are high flow Magnaflows. I never though about anything inside the cats, can you tell if you take the pipe off and shake it? The cats don't have many miles on them so I wouldn't think there should be any issues but I have seen stranger things happen.

i am not too sure on shaking it. i suppose you could. hopefully the 'night crew' will come on soon and chime in for you

 

[Kilgore Trout]

I also think it is the cats breaking up inside.

 

[Dr Jay]

Man that's really disappointing if it is the cats, I paid so much for the h pipe and I haven't put that many miles on it. Is there any way to tell for sure?

 

[patman0911]

Get under the car and bang on them and listen for stuff rattling around in them. It was pretty obvious when the cat in our Lesabre went bad - it was rattling like a can of marbles. When I cut it out, chunks of honeycomb fell out. Of course, it rattled from idle right up to the clogged cat imposed redline.

You haven't been running a rich have you? You can foul and mess up cats pretty fast that way if you're running rich all the time.

I'd take a look at those heat shields and look and see if anything under there is loose or close enough to the body, frame, trans, driveshaft, or whatever that it could potentially be vibrating against it.

 

[Dr Jay]

I'm not running rich but the spacing around the drivers cat is really tight. When I stomp on it wouldn't that drivers cat move up and out a bit with the engine movement? If so, maybe that shield is making slight contact??