TheRook

So i started noticing this loud rattle after the weather got cooler, but i usually drive with the radio on so i hadn't noticed it til thursday. The rattle usually goes on from 3700rpm and again at 4000rpm, but last night the weather was a little cooler than normal and i could hear it intermittently at idle and constantly around 2500rpm. I put the car on a jack and started tapping around the exhaust but didn't hear anything really, the car was cold. I warmed up the car and checked again, this time i could hear some rattling on/in the cat. The heat shield is missing some bolts but i didn't see it move as if it were bouncing on the cat. I found a video of an s2000 with a busted cat but the noise heard while he's hitting it is deeper than mine, but it still has that rolling rattle at the end. I'm just not sure if it's the cat or heat shield (lack of experience), and hoping you guys could help me figure it out.

Long story short, I heard a metallic rattle, can't tell if it's the cat or the heat shield. Anyone can help me out?

video 1
http://youtu.be/Cb4T-Qvw4F0

video 2 (rattle goes on a bit longer after hitting it)
http://youtu.be/Y2ZfbTQSucE

video 3 (car on and rev to about 4k, noise starts around 31)
http://youtu.be/jZgNQ4Re7vM

and here is the video for comparison where the owner diagnosed it as a busted cat
http://youtu.be/_jk48X85LsM

AZfury

i would just try taking the shields off and try listening again since you said the heatshield is missing bolts it WOULD def. rattle

Car Analogy

When I bought my S it had this awful rattle from CAT area. It was so bad I thought it had to be internal to CAT, not just the heat shield. A PO had welded in a really cheap generic CAT. They hacked up the stock exhaust to do it, removing the flange the rest of the stock exhaust. So fixing it (back to stock or aftermarket bolt in CAT) meant replacing the whole exhaust.

So while I was gathering the parts, I was under the car looking at something else, and I saw where the heat shield was lose way up in back. So I figured what the heck, and drilled some holes to pop-rivit the shield in place, noise gone. I went through emssions that way and passed, since it took a while to get the parts together (I wanted to replace the cheapo CAT no matter what).

My point is try mounting the heat shield more solidly first. Its pretty easy, it will tell you definitively if its internal or not and might just fix your problem.

TheRook

Thanks for the replies. Hopefully I'll have time to try messing with the cat and heat shield tomorrow. Would there be any consequences if I removed it completely? I'm thinking it may not bolt back together again since the bolt holes/mounting areas are pretty rusty.

AZfury

no consequences other than feeling a little extra heat from the center console area.

Car Analogy

I'd be wary of too much heat igniting the undercoating. Find a way to get that shield back on. If bolt holes rusted through, try JB weld.

darcyw

I've run no heat shields on my Civic SIR for years -since they rusted off long ago. And as my friends will tell you, i'm usually high from spraying undercoating on my car for corrosion protection. I have had no ill effects…yet.

darcy

mirabileboy

have you considered just buying a test pipe?

AZfury

you would be amazed about how many people have no heatshields on they're cat, let alone all the people here who have test pipes on they're s2k's.....no problems that ive heard of and i work on cars for a living.

Car Analogy

Well by definition a test pipe isn't going to get as hot as a cat. Cat is performing chemical reactions that generate heat above what just exhaust is generating.

I guess I look at like those recalls you see with other cars every once in a while for issue that can cause engine fire. You didn't hear about a single person having the issue with the fire, so do you tell people to ignore the recall? It can happen, it has happened, better safe than sorry.