Catalytic Rattle

[white98]

My 98 has been making a horrible rattling sound from underneath, and my mechanic says that it's probably coming from the catalytic converter as a result of loose pieces or something. Has anyone else experienced this problem? Should I get a factory replacement or should I go aftermarket...My only mods as of now are dual flowmmaster. Thanks

[blackfire99]

whatever you do, don't touch it til you decide, it is covered under warranty for 8 year/80000mi...don't make the mistake i did, from what i have read, the catco is best performing and only $50 from summit...

[Predator Bird]

my catco had a bad rattle, the heat shield was loose so i took it off and the rattle stopped. if its a factory cat i don't really know, unless its the inside going bad.

[silicuda]

i had the same damn thing happen, it was cuz of a lose bolt, and the isolation between the plates wuz missing or something so when the car metal and the cat touched it would make this really bad sound....

check the mounting bolts, and stuff.. maybe there is a plastic thing that goes between there to keep the car's frame from touching the cat.. i dunno but i know mine was caused by something being lose

[jhkcam]

Just got done going through the same thing. Untolerable rattle from under the car. The exhaust guy thought it was the catalytic converter at first, but it turned out to be the mounting brackets for my catback. One of the bolts was loose and rattling like crazy. As of Monday it appears to be fixed.

-Justin

[UNFNick2k]

had the same problem and i thought it was the cat/y pipe. turns out it was the joint off the S pipe from the cat, the clamp was not as tight as it shoudl have been

[12secondv6]

Well, inside the cat is all riddled with a honeycomb center. This is where the catalyst continues the combustion process for a more friendly emmissioned car.
My bro's jeep: his honey comb just fell apart inside
The bird: I replaced them before the honey comb went but I removed the heat shields due to rattles.

You need to figure out if it is just a heatr shield or the honey comb inside bit.
If it is the heat shield any muffler shop can just tac weld it back on
If it is the honey comb you can just continue to drive around and eventually it will break up and come out of the exhaust or just replace it with a Catco $55 high flow version from www.summitracing.com

[silvachris1]

I had a tiny piece of gravel between the heat shield and the Cat. I wouldn't fit throught the hole and I was baffled at how it even got there. Anyways, I jacked the car up, climbed under and started tapping it witha hammer trying to locate the rattle, when that didn't fix it, I just started pounding it. Finally, I saw the gravel and couldn't get it out. So I grabbed the closest screw driver I could find, and widened out one of the holes, then tapped on the heat shield till the gravel bounced over to the hole and fell out. Then, I found another rattle in the exhaust, the heat shield on the I-pipe had broken right where it goes under the clamp. It was a horrible, horrible noise. So I drove to the hardware store and bought a hose clamp for like 2 bucks, and was gonna put it on untill I get a new exhaust. But on the way home, I heard the rattle, and then a clank sound. When I got back under it again, the heat shield was gone. Go figure. No more rattles though. lol

[Mr. Spock]

If the heat shield rattles and you actually want to keep it get some hose clamps link em end to end and tighten around the heat shield/ cat.

[white98]

Ok...looks like it's definitely the insides of the cat that are rattling and not the heat shield. My car has 65K so I could get the free factory replacement. Would the Catco provide significant gains in performance? Or would it make my flowmaster sound a little better? What would you guys do? Thanks, Justin