Knocking Rattle Sound - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 3 (permalink) Old 12-19-2010, 05:14 AM Thread Starter
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Knocking Rattle Sound

I'm hearing a knocking sound coming from underneath at the rear part of the car. The rattle/knocking has been there since the car was new. It doesn't occur often and it seems to happen at around 35 mph when decelerating.

My guess is it's the exhaust system but the exhaust plumbing doesn't feel loose (although I haven't gotten underneath to really examine it carefully)

Any ideas?

2010 Cobalt XFE
2006 Chevy Colorado 4x4
2005 Toyota Corolla
2013 Kubota M5640 SUD
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post #2 of 3 (permalink) Old 12-19-2010, 09:19 AM
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I have a rattle noise from the rear that I though was from underneath. I found that the tin shield they have covering the fuel tank was not tight on the passenger side. I stuffed some foam rubber in the shield and fuel tank to stop it from being loose. turns out the rattle is still there but I think I eliminated one rattle anyway lol.

My next idea is that it's coming from the rear deck inside the car. that thing is loose and flops around easily. I just haven't gotten around to messing with it yet.
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post #3 of 3 (permalink) Old 12-20-2010, 03:07 AM Thread Starter
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Thanks Blaze...I need to get under there and have a look around. I'll check around the gas tank for that shield.

It seems to happen most oftern when I'm letting off the gas to shift from 3rd to 4th or when I decelerate quickly from aound 40 mph or so. A few years back I had a Nissan pickup that developed a similar noise. In that case the exhaust pipe was knocking against the frame due to a missing hanger. I doubt that I have a missing exhaust hanger but again, I need to get under there and poke around.

2010 Cobalt XFE
2006 Chevy Colorado 4x4
2005 Toyota Corolla
2013 Kubota M5640 SUD
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