Noise from Rear

Fossil1

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The car is a 2005 180K C class saloon. My problem relates to a 'Bonking' noise from the back of the car which is just 4 years old and has covered 17,000 miles. I first of all thought it was the spare wheel or the floor cover but I have now eliminated these. I think it actually comes from the rear off side. It is only noticable when going over a sharp bump or manhole cover. It may be just a figment of my imagination but the noise seems to disappear for a short time after the vehicle has been on a ramp with the wheels hanging down as was the case during it's recent MOT. Any ideas? :confused:
 

walkenblue

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The car is a 2005 180K C class saloon. My problem relates to a 'Bonking' noise from the back of the car which is just 4 years old and has covered 17,000 miles. I first of all thought it was the spare wheel or the floor cover but I have now eliminated these. I think it actually comes from the rear off side. It is only noticable when going over a sharp bump or manhole cover. It may be just a figment of my imagination but the noise seems to disappear for a short time after the vehicle has been on a ramp with the wheels hanging down as was the case during it's recent MOT. Any ideas? :confused:

My sibling has same noise , some may say it could be the shocks.But car only mot'd a few weeks ago ,It is annoying as it does come and go, it was noticed after a tyre was replaced ,car taken back to tyre place and checked to see if maybe the springs had not seated right,there is no change .I am sure you/we will get good advice here........
 

television

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A broken spring maybe,,should not be bushes at that mileage
 

grober

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Broken spring is a distinct possibility. They tend to break at the end where they are seated in the suspension arm and this is difficult to see even from underneath the car. You need to inspect the spring by jacking up the car+removing the wheel. You can then look down on the recess in the suspension arm the spring locates in using a strong torch or inspection light. You need to look very carefully. I have had several cars which have passed the MOT with springs that later turned out to be broken but were not picked upon the inspection.
 
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walkenblue

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Exhaust been checked by tyre guys, it looks like back up in the air and check springs thoroughly..
 
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Fossil1

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First of all many thanks for all the suggestions. My son-in -law is a mechanic and has had the car on the ramp and checked for broken springs, leaking shock absorbers, exhaust touching bodywork etc. There are no signs of any scuffing or marks where other components have touched. As I said in the original post when it comes down from the ramp after the wheels have been hanging the noise goes for a short while. Never been driven over rough ground or with a heavy load. Usually just me and 'Her in doors' on a normal road.
 

mickt

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loose bolt or bush on rear subframe, or childs toy under the rear seat:rolleyes:
 

teabag

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The car is a 2005 180K C class saloon. My problem relates to a 'Bonking' noise from the back of the car, It may be just a figment of my imagination but the noise seems to disappear for a short time . Any ideas? :confused:

Have you checked the rear seats for any unwanted passengers.

Sorry.... Couldn't resist it, but it does sound like a broken spring
 
A

andy@pcd-ltd

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I have had this noise a few times when a car has been on a ramp especially C classes.

The spring jumps out of its locating portion of the lower arm and then touches on the rear of the arm and makes a noise when you go over bumps.

The way i get them back in is to compress the spring slightly with a spring compressor and then use a lever bar to push the spring bsck into place
 

salmanhamid

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I had exactly the same problem and it was a broken spring.
 

The Hooded Claw

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Completely off topic here but


Whenever I make a "Noise from my Rear" just get a slap on back-o-me ead from Marie!!!!!!!!!!!!!
 
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Fossil1

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Problem now solved. My son in law was positive it was the O/S rear shock absorber. In the end I paid for a new unit and he fitted it. Noise gone. The old unit when examined had a lot of 'free play' on it thus causing the sound on sharp bumps and not on undulating surfaces. Not good for 20,000 miles.
 

HelpThisDude

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Son in law deserves a pat on the back :)
 

JEZ.S320L

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Problem now solved. My son in law was positive it was the O/S rear shock absorber. In the end I paid for a new unit and he fitted it. Noise gone. The old unit when examined had a lot of 'free play' on it thus causing the sound on sharp bumps and not on undulating surfaces. Not good for 20,000 miles.

**puts hand up** I was always under the impression, that they should always be replaced in pairs, not just a single unit. Yes/No?
 

turbopete

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**puts hand up** I was always under the impression, that they should always be replaced in pairs, not just a single unit. Yes/No?

probably should be, but seldom are.
 

grober

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Have to say the sound will still have come from the spring bottoming out not the shocker itself. They don't make a sound normally even when they are damaged. Hope that's your problem solved now. :D
 
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Fossil1

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Have to say the sound will still have come from the spring bottoming out not the shocker itself. They don't make a sound normally even when they are damaged. Hope that's your problem solved now. :D
I believe the sound was coming when the car body went up over a sharp bump and then came back to that point where the shock absorber was taking up the damping action. The free play was in the top 2 -3 inches. Hope I have explained myself OK. Any way I am now happy and have a Mercedes that rides the bumps as it should, QUIETLY.
 


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