Exhaust Rattle at Low RPMs

Hey guys,

Tried searching before I posted, but apparently "exhaust rattle" is in a lot of threads somehow. I'm guessing this could be somewhat of a common issue.

Here's the issue. This only happens once in a while, but frequently enough for me to get annoyed with it.

At low RPMs, usually at the beginning of a gear, there's a rattle that comes from the exhaust for about 3 seconds, then stops.

I have an 02 WRX with an aftermarket catback exhaust (of course just started noticing it after I upgraded from stock). The piping from the catback to the exhaust is wider in diameter than stock, naturally. So my guess is, that pipe is rattling against the underbody somewhere or against a heat shield.

Today I got behind the car and shook the hell out of the muffler and didn't hear a noise whatsoever. I'm guessing the engine shudder at low RPMs could cause a more hefty shake than I could. I don't think it's coming from within the exhaust, since I didn't hear it when I shook it, and since it's only happening at certain times.

Has anyone had this issue? My only guess is it's hitting the underbody somewhere when the engine is shuddering at low RPMs. How would I fix that? Exhaust wrap?

Thanks in advance!

 

If you can't see where it could be rubbing under the car there's a number of things an exhaust rattle could be. Might be a loose perf tube in a resonator or muffler. Could also be a broken or loose core in your catalytic converter. That's a couple things to look/ listen for.

 

Readymix has this same thing, he said something about it being in the spot where it's supposed to bolt onto the transmission. He usually let it just hang, but as soon as he bolted it up there it started rattling, and yes, it's at low RPMs. Most noticeable when shifting.

He thinks he just has to get better bolts for it, because the exhaust is too wide for the bolts they sent him. It doesn't clamp down right. I'll let him chime in on this when he gets back later tonight, but if it's the same thing he's got, it's not causing any damage - other than being really annoying

 

yeah, I would say part of it is the Minnasota rust, (that is, if it's a MN car)

or more like 60/40.

rattle over the internet, it's a hard one.

 

Any idea where about the noise is from? Middle of the car or further back?

 

It's hard to tell, but I think it's occurring further back. I can't hear it standing outside the car b/c it doesn't happen at idle, and with my windows down I can't tell where exactly it's coming from, I can just tell it's coming from out the window, lol.

But it does sound more like it's coming from the back end.

 

I don't think it's rust however, the CBE is only a couple months old.

 

What brand cat back is it and did it re-use all of the factory exhaust hangers?

 

SRS and yes, factory hangers. I'm reading that I might have to go with the KartBoy long hangers.

 

I had a srs for a while. Fitment was pretty good but the packing in the muffler blew out pretty quick, which kind of makes me lean more towards the perferated tube rattling in the muffler. Are you using the silencer in the tip. If not I would look in the pipe and check if there is any packing left or if the perf tube is loose.

 

No silencer. Today when I shook it I looked in as well, didn't see anything out of the ordinary. And if something was loose, I'm sure I would have heard something rattle when I shook it. Literally heard no rattling at all when I vigorously shook it.

 

I'm guessing its a stretched or worn hanger.