Banging sound when car is not running
Thread Starter
Former Vendor of MBWorld
Joined: Jan 2007
Posts: 3,193
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From: Glendale Arizona
C55,SL55,C63
Banging sound when car is not running
My C55 makes a banging sound when i shut the car off. I let it sit for a bit them a loud bang comes from under the car its not near the engine so i think its coming from the exhaust. example... If i shut my car off get out and wait the car will make a loud bang and if people are near my car ask "WTF was that?" it sounds like its coming from the exhaust somewhere. any idea's
Member
Joined: Jan 2007
Posts: 108
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From: Texas
06 C55
mine too
it is either the exhaust or the heat sink on the rear end. I notice it tends to come from the back of the car.
I don't worry about it because I know what it is, but I'll admit I've never heard another car as load as the C55.
Don't know if the lesser C's do this too.
I don't worry about it because I know what it is, but I'll admit I've never heard another car as load as the C55.
Don't know if the lesser C's do this too.
Member
Joined: Jan 2008
Posts: 197
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From: Houston, TX
2005 C55 AMG
Have you considered it might be possessed? Maybe you need to perform an exorcism! 
Okay, okay, sorry, I couldn't resist.
I agree it's a heat related issue, and likely due to the expansion/contraction characteristic of metal when heated and cooled. I'm even wondering if it might be something in a catalytic converter, possibly igniting some unburnt fuel or shifting catalyst material? Just a thought...
My car makes heat related noises upon shutoff, but it's a very minor "tick tick tick tick" sound that I've heard other vehicles make related to shutting off the hot component. However, mine is a typical siund and not loud at all.
Yours sounds like a little more is happening there. Especially if it draws attention like that. It might warrant a view from underneath, via putting it on a lift or using a floor jack, and get underneath to give a closer listen/view.
Okay, okay, sorry, I couldn't resist.
I agree it's a heat related issue, and likely due to the expansion/contraction characteristic of metal when heated and cooled. I'm even wondering if it might be something in a catalytic converter, possibly igniting some unburnt fuel or shifting catalyst material? Just a thought...
My car makes heat related noises upon shutoff, but it's a very minor "tick tick tick tick" sound that I've heard other vehicles make related to shutting off the hot component. However, mine is a typical siund and not loud at all.
Yours sounds like a little more is happening there. Especially if it draws attention like that. It might warrant a view from underneath, via putting it on a lift or using a floor jack, and get underneath to give a closer listen/view.
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Member
Joined: Jun 2006
Posts: 124
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From: Canada
c32 AMG
This is normal.. mine gets the tick tick tick sound. Even BMW's do this especially the M series. These cars are meant to be driven hard and this generates alot of heat. Hence the expansion and contraction of metal. 
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Member
Joined: Jan 2007
Posts: 108
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From: Texas
06 C55
just to clarify
Although I am not the original poster....just to clarify...
I've owned two BMW's and an Audi. They all 'ticked'.
This is not a tick. This is a fricken 'bang'.
It does it almost every day, about 5-10 minutes after shutdown.
I am not worried about it - but I just wanted to clarify that it is not a 'tick tick'. Oh, but mine ticks too, but it also makes this loud bang. Maybe two or three of them on cooldown.
I've owned two BMW's and an Audi. They all 'ticked'.
This is not a tick. This is a fricken 'bang'.
It does it almost every day, about 5-10 minutes after shutdown.
I am not worried about it - but I just wanted to clarify that it is not a 'tick tick'. Oh, but mine ticks too, but it also makes this loud bang. Maybe two or three of them on cooldown.
Last edited by tech_frog; Mar 21, 2008 at 09:44 PM.
Member
Joined: Jan 2008
Posts: 197
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From: Houston, TX
2005 C55 AMG
I'm sticking with my theory that something is causing an ignition in the exhaust, ie unburnt fuel left on the hot catalyst material. However it's still puzzling as to why this would be happening, and obviously it should not be.
I'd love to hear input from one of the MB Tech's on the forum regarding this.
I'd love to hear input from one of the MB Tech's on the forum regarding this.
Member
Joined: Jan 2008
Posts: 197
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From: Houston, TX
2005 C55 AMG
If he does test it this way, I recommend using something that can muffle the sound as HAZY1 suggests, but that will also have enough give to allow it to be discharged out the exhaust. In other words, make sure it acts as the "pop off" valve and does not contain the alleged explosion internally. Stay away from using a potato or the likes.
Just a thought leaning toward the conservative side...
Super Member
Joined: Sep 2007
Posts: 784
Likes: 1
From: Miami
Bicycle
Its the cats. After I did the headers and custom exhaust it never did it again. The tick is normal but the pop was werd. It scared the s!!t out of me. I removed the resonator first and it still did it but as soon as i replaced the cats for performance cats that was the end of that.
Member
Joined: Jan 2008
Posts: 197
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From: Houston, TX
2005 C55 AMG
By what I understand, there is a factory recall on the cats, and the dealer will replace them under warranty. My friend just had his done on his '05 C55 without any questions from the dealer. He was still under the factory warranty, but if it's a recall item they should replace them for free regardless of warranty status.
Federal Law mandates the vehicle's emissions catalyst system be covered under warranty for any defects for 8 years or 80,000 miles, whichever comes first.
I definitely think it'd be worth you checking with your local dealership. Just give them your VIN number and they can determine if yours were ever replaced, but as stated above they should be covered regardless, if they've become faulty again.
Federal Law mandates the vehicle's emissions catalyst system be covered under warranty for any defects for 8 years or 80,000 miles, whichever comes first.
I definitely think it'd be worth you checking with your local dealership. Just give them your VIN number and they can determine if yours were ever replaced, but as stated above they should be covered regardless, if they've become faulty again.
Thread Starter
Former Vendor of MBWorld
Joined: Jan 2007
Posts: 3,193
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From: Glendale Arizona
C55,SL55,C63
Member
Joined: Jan 2007
Posts: 108
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From: Texas
06 C55
It is not residue fuel
I am 99.9999% sure this is not residue fuel. It is not coming out of the tailpipe. It is simple thermal expansion (or contraction...as the case may be).
Probably the cat(s).
I am not worried about it, though, I am soon ready for Service 1......I'll ask them.
Probably the cat(s).
I am not worried about it, though, I am soon ready for Service 1......I'll ask them.
Senior Member
Joined: Sep 2006
Posts: 455
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From: P'cola, FL
'03 E55
I'd be a bit concerned about this method, in that it runs the risk of a restricted internal explosion (albeit small) that cannot ventilate out the tail pipe, and possibly causing other damage.
If he does test it this way, I recommend using something that can muffle the sound as HAZY1 suggests, but that will also have enough give to allow it to be discharged out the exhaust. In other words, make sure it acts as the "pop off" valve and does not contain the alleged explosion internally. Stay away from using a potato or the likes.
Just a thought leaning toward the conservative side...
If he does test it this way, I recommend using something that can muffle the sound as HAZY1 suggests, but that will also have enough give to allow it to be discharged out the exhaust. In other words, make sure it acts as the "pop off" valve and does not contain the alleged explosion internally. Stay away from using a potato or the likes.
Just a thought leaning toward the conservative side...
