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I've been meaning to dig into this dilema for a couple of years but its not until today that it really erked me enough to ask some experts (you guys and gals):

-I have a 2001 Civic Coupe / LX / SIDE SRS and many years ago I upgraded my exhaust system by installing a Thermal R&D Catback exhaust (the same one that DerekCEO (original owner of this forum) had).

-Here is the problem: There is noticeable wiggle room between a section of the exhaust pipe and the chasis of the car; the common impact point for the pipe to hit the chasis is right under my Emergency Brake handle.

-This wiggle room is never a problem and never rattles UNLESS its raining outside, then, for some odd reason, the pipe starts vibrating to hell and creates a horrible loud noise right under my break handle because the pipe is hitting the chasis.

-So the options are:

a. Put something in between the pipe and the chasis, something that can withstand the heat, like thermal wrap, which i tried. The problem is that a lowered car is prone to rubbing up against stuff and lo and behold, the thermal wrap didnt last past a month.

b. Clamp the pipe to the chasis to prevent further movement. This is actually my next option but I'm not even sure where to start as far as what kind of clamp/screws and where on the chasis to drill it into.

-Finally, WHY does water make my exhaust goes crazy!? Has anyone ever experienced this? Is there something I can do to prevent this rattle in the first place?

Thanks for reading and I'm looking forward to your thoughts!

 
Rep Power: 811

water makes the metal expand or something, its actually an issue with some oem exhausts too and the fix honda put out was to change it with a different pipe that sits further from the car body. a muffler shop may be able to slightly bend the pipe and give you more room.

 
Rep Power: 230

let me be clear on this. is it bumping underneath the passenger side about half way back, and right under the heat shield?

me and many others have had this problem. im guessing on your catback system it has a flange where two of the pipes connect right under that heat shield like our systems do? what i did is just bent the heatshield a bit and notched out a chunk of it in the shape of a 'V' on right where the flange is. it got rid of most of the problem.

 
Rep Power: 230

My first exhaust set-up did this. I simply took a pry bar to it after a long drive a couple times and bam! fixed.

 
Rep Power: 323

i remember alot of people having this porblem years ago. the solution is remove or bend your heatshield so it has some more clearence. removing it will not adversly effect your car in any way. i havnt had mine on since 2002 lol

 
Rep Power: 209

To answer your question why this is happening, my guess is that in the rain the bottom or lower side of the pipe gets wetter than the top and is therefore cooler. The difference in temperature causes a slight difference in expansion causing the pipe to arc slightly upward. Under other conditions the pipe heats and cools at the same rate on all sides and maintains it's position.