loud knocking noise under the car
Thread Starter
Joined: Oct 2006
Posts: 35
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loud knocking noise under the car
i've heard it twice and both times it was while it was raining and i was driving down the road. It almost sounds like something is rattling but it's just so loud...i haven't gotten under the car to check for loose exhaust piping but thats my next plan. And my muffler is showing it's age with rust holes and if i'm in park of neutral and gas it and let it fall back to idle you can hear the muffler sputter on the way back down....exhaust leak?
Legend
Joined: Feb 2006
Posts: 9,284
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From: mendota, illinois
RE: loud knocking noise under the car
my step dads 99 neon sport ran real bad when it rained out and it hit some puddles.....it would knock and smoke real bad....then i would shut it off and let it sit for a couple minuites and it would run fun.....if i remember right i think the cause was the EGR valve, but im not positive since it was almost 5 years ago.....but either way, it was because sumthing was getting wet
Legend
Joined: Apr 2006
Posts: 9,112
Likes: 1
From: Spring, TX
RE: loud knocking noise under the car
This is probably your answer...
This happens when substantial water splashes onto the exhaust piping, causing it to cool suddenly and thus distort. If it is not tightly secured in all of the rubber hangers, the pipe may rotate enough to vibrate against the sheet metal heat guards under the car. The resulting noise should disappear when the pipe returns to a consistent temperature and resumes its original shape.