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Okay everyone, I know that this has been addressed a dozen times here but I still do not have a definate answer as to whats going on. I have a Greddy EVO 2 and that is the only mod so far. I live in Kansas City and it rained today. My exhaust started making that bumping sound and was really annoying. My question is this, why does water affect the exhaust in this manner. What does it do to the pipes that make them bump and why doesn't it do this when it is dry. Lastly, HOW DO I FIX IT?!?!?!? Everything underneath is fine, I just put it on a week and a half ago. Thaks for your help.

 
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you mean like when your driving in the rain it vibrates underneath the car right? yea mine does that to....no idea why

 
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u cant fix it

what happenes is that your exhaust is hot, when the water hits it, it starts boiling (ie crakeling).. also because of the change in temperature between the exhaust gases and the water cause the metal pipes to bend slightly (expand, contact, laws of physics) so it makes that sound

u have to leanr to get used to it

 
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hmmm not sure maybe the muffler bearings are getting wet jk lol

 
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Thanks PLAYER. At least I have an idea why. Is there anything I can do to make it less noisey? Also, I can hear the pipes banging against something. I would assume it is banging against the rear axle. Is there anything I can do to make that stop.

 
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fortunately that doesnt happen on my HP racing Jspec catback it has been raining all week here and no annoyng sound except the not too loud deep sound i love this exhaust

 
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yea hold a hammer... aim at it..close ur eyes.. and hit as hard as u can
if u hit ur body part scream if u hit something else run....lol

 
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I have an EVO and it does it only when it rains. The vibration is not at the rear axle, atleast not on mine but it is occuring right after the cat going towards the back. The pipe is hitting the under body right underneath the shifter. Like I said, that is what my car does when it rains. I have tried bending it but nothing. I will deal with the noise before I damage my exhaust beyond repair. Just have to get used to it.

A flaw in an excellent exhaust.

 
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^^^^ lol!!! ^^^^

 
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I have an EVO I also. And I know why it makes that loud vibrating sound like your tranny is gonna fall apart or come throught the floorpan.......I researched the problem and found the answer.

 
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Is there an answer? if so how do you fix it?

 
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Of course there is an answer.......what's in it for me?

 
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knowing that you helped someone out.

 
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lol.. mine makes noise too its a Megan catback, but its not that loud or annoying it always changes in sound when temp changes/rain/etc.. I wonder how it'll sound in the winter..

 
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mine simple... just put the pieces on its right place double check just to make sure everythings fine... that's all natural though, i think that bumping noise, your pipe hits the heatshield under your body... take time to observe, you'll be good.

 
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Your car is going to blow...
and they are all going to laugh at you

kidding.
what player said is correct

 
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Is it only after you drive through a puddle? How long does the noise last?

 
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yes it is. also, i just put up a new post about some info I found out. A guy at a local shop told me that it was the rubber hangers slipping around

 
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what do you think, I talked to a number of different people and they said that sounds right

 
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Honda put out a bulletin about it on the 2001 models. I have a 2002 and had the same problem. Refer to my posts in this thread. Honda fixed it for me. It was the b-pipe heat shield. It looks like you can't access the bulletin on-line anymore, but it is Bulletin number 202 put out in Feb. '02. I have it at home and can scan it in when I have a chance

 
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what is the b-pipe heat shield? is that the heat shield above the mid-section? did you get specifics as to what they did to fix it, and did they give you any heck about fixing it because you have an aftermarket exhaust? I found the TSB about it on Edmunds. Should I just call the dealer?

 
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Just an edjucated guess, but maybe the water is being trapped around the heat shield area... then it boils, and the water boiling is actually your rattle? The rattling does go away on my car, then it starts again, then it goes away, then it starts again, then it goes away, then it starts again.

I could be wrong, and probably am. Dont listen to me.

 
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They replaced the pipe, since the heat shield is attached to it. The bulletin shows what part number they need to replace it with. Call the dealer and see what they say. I had to take the service manager for a ride in the rain so he could hear it for himself before they did the work.

 
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so, they replaced the whole pipe? is there a different pipe aside from the pipe that comes off the cat and then leads to the muffler. Because I can't replace that, it's part of my exhaust (it the mid-section)

 
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It's actually called Thermal Shock. The heat shield gets hot(obviously), and when you drive through a puddle the water cools the metal so fast that it changes the shape of it causing it to rattle against the exhaust.

 
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how long did it take them to fix it and did they cover under warranty since you have aftermarket exhaust?