Exhaust movement / bad clunking in rear- *dealer fixed* - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-22-2007, 02:56 PM   #1
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Default Exhaust movement / bad clunking in rear- *dealer fixed*

I've been noticing some bad clunking in the rear of my GXP, like a big brick in the trunk bouncing around. I checked the spare tire, battery mount, and anything I could grab to shake and find the source.... nothing. Then I found that I can move the whole exhaust system and get it to smack against the frame. The hangers have THAT much movement in them. None of them are broken or loose, they just have a lot of left and right travel.
The exhaust seems to clang when I hit it against the frame, which I'm not sure is the same clunk I hear when I drive. I did notice the clunking is much worse when my kids are in the back seat.
I did a search and found nothing. Can anyone else shake their exhaust tips back and forth enough to get the mufflers or pipes to smack the car frame?
Any other clunk sources you can think of that I should investigate?
My car is under warranty 14K on it, but this is one of those things that I would rather investigate before I hassle with Mr. G.M. Nofix.
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Old 04-22-2007, 07:46 PM   #2
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The exhaust on my GXP has maybe a couple inches movement either way, not even close to hitting off the frame though.
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Old 04-23-2007, 09:29 PM   #3
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How about the top mounting points of the rear shocks? They bolt up on the inside of the trunk. They are hidden by carpet and have black rubber covers on top of them.




I had water coming in through the wheel well on mine. I sprayed undercoating around both rear shocks where they come through to keep the water out.
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Old 04-23-2007, 11:27 PM   #4
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blubyu, are you suggesting that the shock/struts might be loose and clunking? That'* an unnerving idea on a newer car. Would you be able to tell with the weight of the vehicle on the struts, and just by inspection? It seems you might need the rear on jackstands or something.
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Old 04-24-2007, 10:09 PM   #5
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Quote:
Originally Posted by skregal
blubyu, are you suggesting that the shock/struts might be loose and clunking? That'* an unnerving idea on a newer car. Would you be able to tell with the weight of the vehicle on the struts, and just by inspection? It seems you might need the rear on jack-stands or something.
I'm just stating it would be worth inspecting. My issue was water, not noise. If I had a loud noise like that. I would definitely unload the back end and put a piece of wood under the rear tires like a pry-bar to try and re-create the noise.

I had a decent amount of water coming up through the passenger side shock which ultimately would have lead to corrosion.

Is it when you go over bumps?

Warranty or not, anything beats a dealer visit. If they don't find it, you could be making several dealer visits. It'* always nicer when you can take it in knowing exactly what is wrong.
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Old 04-24-2007, 11:07 PM   #6
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The clunk only happens when I hit a series of bumps. That led me to believe it was the exhaust at first, getting the right amount of momentum, swinging back and forth. When I was able to force the exhaust to make contact, I knew that wasn't right. But the sound really doesn't seem the same, it'* hard to tell from driving compared to laying underneath the car. I'll check those struts this weekend.
It really sounds more like something is loose and the exhaust is actually really tight, even though it has some movement. What I'm saying is the exhaust may hit once but not 4 or 5 times. I hear "clunkity, clunkity, clunk, clunk".....
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Old 04-24-2007, 11:36 PM   #7
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It would be a good idea to check the shock mounts. I would think that they would have been better on the newer cars, but the shock shaft broke through the mount on my car with less than 50k miles on it. It was quite obvious just by looking at it from the trunk. Pull the cover off to inspect it.
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Old 04-27-2007, 10:13 AM   #8
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The shock mounts are tight, I just checked them. I really can't find any other suspension part that is loose. I'm back to the exhaust hangers. I know you guys can't be much help on a car you can't see or touch with this type of problem. There aren't a lot of GXPs to get some history of common problems, either. Thanks just the same.
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Old 04-27-2007, 10:26 AM   #9
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Yes it is a toughy especially with so few GXP'* and still rather new, mine is just over a year off the lot. I checked my exhaust and it is tight, really tight for the roads here and the 1/2 mile driway from hell. All i could think of was exhaust, broken rear coil spring, shock mount, or perhaps you lost one of the rubberspring bushings. Is the battery hold down in place?
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Old 04-27-2007, 02:34 PM   #10
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my 2000 SSEi exhaust hit when i went over speed bumps at an angle(sway side to side).
i had my exhaust guy put a mount on the exhaust that went on horizontal (just like the
vertical mounts) but on its side, no more noise from my exhaust pipe hitting the side of
the heat shield. the mount went on at the rear of the single pipe right before the split.
hope this helps.

ROD
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