Weird "knocking" sound after driving

royalnewjersey · 10-13-2010, 01:52 PM

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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royalnewjersey · 10-13-2010, 02:03 PM

YouTube - After Driving

RaineMan · 10-13-2010, 03:02 PM

Exhaust cooling... mine does the same thing. You are fine.

RaceFaceXC · 10-13-2010, 10:07 PM

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.

Bluefoton · 10-17-2010, 06:33 PM

^ very eloquently put!!!!

RaceFaceXC · 10-19-2010, 10:43 PM

I thought I butchered it with a spoon. but thats why I turn wrenches instead of writing for a living. Thanks, though!

10-13-2010, 01:52 PM	#1
royalnewjersey Scooby Newbie Member#: 250954 Join Date: Jul 2010 Chapter/Region: NWIC Vehicle: 2013 WRX Hatch WRB - On Order	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. * Registered users of the site do not see these ads.

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10-13-2010, 03:02 PM	#3
RaineMan Scooby Specialist Member#: 256727 Join Date: Sep 2010 Chapter/Region: RMIC Location: SL,UT Vehicle: 2007 2.5I Wagon Silver	Exhaust cooling... mine does the same thing. You are fine.

10-13-2010, 10:07 PM	#4
RaceFaceXC Scooby Specialist Member#: 165749 Join Date: Dec 2007 Chapter/Region: South East Location: stupid Florida Vehicle: 2007 No YELLING on the bus!	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.

10-17-2010, 06:33 PM	#5
Bluefoton Scooby Specialist Member#: 141373 Join Date: Feb 2007 Chapter/Region: E. Canada Location: Quebec, QC Vehicle: 2008 2.5i-hatch - now with a HID retrofit	^ very eloquently put!!!!

10-19-2010, 10:43 PM	#6
RaceFaceXC Scooby Specialist Member#: 165749 Join Date: Dec 2007 Chapter/Region: South East Location: stupid Florida Vehicle: 2007 No YELLING on the bus!	I thought I butchered it with a spoon. but thats why I turn wrenches instead of writing for a living. Thanks, though!