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Old 10-13-2010, 01:52 PM   #1
royalnewjersey
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Default Weird "knocking" sound after driving

So, this might be a stupid question, so be gentle.

After driving my car for about 20 minutes last night I noticed a strange "knocking" / pinging sound coming from my engine bay. The knocks came about once every second with little clicks in between. I heard it after parking while the car was still running. Then I turned the car off and the sound continued.

I think that it sounds like the exhaust expanding / cooling. My old honda had a similar noise after driving for a bit, but this car seems to be much louder.

In any case, what causes this sound? I'm sure it's not harming my car, but I'm just sort of curious. I have a video of the sound, I'll post it once youtube finishes processing

Thanks guys.
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Old 10-13-2010, 02:03 PM   #2
royalnewjersey
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Old 10-13-2010, 03:02 PM   #3
RaineMan
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Exhaust cooling... mine does the same thing. You are fine.
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Old 10-13-2010, 10:07 PM   #4
RaceFaceXC
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the pieces of metal that make up your exhaust and cat and shield your exhaust are made of different materials and heat up and cool at different rates. The thermal expansion/contraction will cause these pieces to move relative to eachother. since they are often attached via crimps/screws/bolts/etc they will build up stress until the force exceeds the strength of the connection and then they move in one quick motion. kinda like a bunch of little earthquakes on your exhaust.
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Old 10-17-2010, 06:33 PM   #5
Bluefoton
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^ very eloquently put!!!!
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Old 10-19-2010, 10:43 PM   #6
RaceFaceXC
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I thought I butchered it with a spoon. but thats why I turn wrenches instead of writing for a living. Thanks, though!
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