W124 Coupe Rear Suspension Knock

[AndyWirral124]

Hi Guys

Im new to the forum, I was hoping someone could help or is having/had a similar experience with their car?

I have a 1995 W124 E320 Coupe, full history, lots of paperwork and has covered 162,000 miles. The issue I have is that my car has a clunk/thud on the rear nearside quarter when going over bumps/pot holes. It almost sounds like something is bottoming out?

Its not a metallic rattle but more of a thud/knock, I am lead to believe it could be sub frame bushes or could be the shock absorber (no signs of Leaking). The car has been to my local Merc specialst who checked the car when I bought it, advisories where new indicator bulb and fog bulb and rear springs (car has Sports suspension option and currently waiting new springs to come directly from Mercedes in germany who are making them as we speak! no stock anywhere!).

I would appreciate some advise as I dont want to go through changing all the bushes to find out its a shock or vise-versa.

Thanks, Andy

 

[WDB124066]

Precisely when does is knock?

Does it tend to do it when accelerating then again when dropping back on the power...? Is it only in corners, or a corner - or just all the time when ever you hit a little bump, big bump only?

Has the car had any replacement rubber in the suspension department, if so what and roughly how many miles on it/them...?

Suspension bushes usually wear out before a shock, you may get 1 1/2 sets of rear bushes to a shock - typically.
They are heavy cars, they love new bushes, shocks and springs, makes it a completely different car. If you have the means and you plan on keeping it and the bushes haven't been done since new, get stuck in and do the lot, it is going to need a refresh at 165000 miles in any case and the result should put a smile on your face.

If you just want to target the offender, try switching from forward to reverse gently with foot on brake the whole time and have someone look at the rear wheel centres - if they shift forward then that's bushes in general, if the front of the subframe drops down in drive then that is front subframe bushes. replacing one or two is never as beneficial as replacing them in sets.

 

[AndyWirral124]

Thanks for your quick reply, the car pulls and drives fine with no knocking under full load or hard acceleration or braking! The knock appears over bumps or pot holes?

Looking through the receipts and history it doesnt say much about rubber bushes, it has had rear shocks at some stage however! In regards to a full bush refurb how much would you be looking at to do this?

Thanks Again.

 

[bolide]

Sounds like subframe bushes to me. The leading bushes are available in a kit from MB complete with new bolts & washers. Used to be £75 / set so they are probably £120-150 now

Make sure the bodywork the front of the subframe bolts to has not rusted away

Nick Froome

 

[AndyWirral124]

Thanks Nick, I have heard many a good word about yourself. I will get my local indy to look at it when he replaces the springs.

Can I ask if I need Sportline bushes as my car has the sports chassis option but isnt a full Sportline model?

Thanks

 

[grober]

If its not the subframe bushes it might be a broken spring. Sometimes these break at the top where they fit into the spring pad- not obvious till the spring is removed /dropped. The new springs should eliminate that possibility.

 

[AndyWirral124]

Thanks Grober,

The springs have been replaced so its not them, the springs in now are standard ones which MB sent by accident! I gotta wait untill December for my Sportline springs to turn up!

I think Nick has put my mind at ease with his opinion of the subframe bushes as it makes sense!

Thanks

 

[bolide]

AFAIK Sports Chassis uses different ARB Bushes to standard cars

The best test I have found is to drop each rear wheel in turn into a deep drain cover. If you get a deep thump it's likely to be subframe bushes

Most of the problems I find are at the front of a W124. Worn wishbone bushes are getting quite common on the six-cylinder cars, as are collapsed engine mounts and split shock absorber top mounts. The back end is simpler in some ways.

When you have the springs off again I'd replace the rubber bushes on the rear shocks and look at the ARB drop links & bushes. Diff mounts tend to go soft and, as a result, the diff input seal ovalises as the diff winds up about under power and the seal starts to leak

Nick Froome

 

[AndyWirral124]

I sorted it over Christmas, the knocking was the shock absorber! It must have suffered an internal fault.

I sussed this out by taking the shock off and driving. hey presto there was no knocking! I replaced the shock and all is good!

 

[WDB124066]

Was it leaking?

Could it have been loose at the mounting points?

 

[RyanAdamB]

Sorry to resurrect an old thread, however I have a similar issue now. I changed the springs as the car was too low, however I have some major clunking going on at the rear - which is becoming extremely annoying! I believe the subframe bushes have worn (having looked at it) however I need to drive the car as it is the only car I have access to.

From a logical point of view, the wheels are too big for my car (18's) and I believe with the raising of the springs - there must be extra stress on the subframe ... that's how I see it anyway (I have no real understanding on how the whole thing works)

It will get to the point where it will just collapse ... so how can it be judged? Do the noises get more prominent?