R129 rear subframe

[SamT]

I'm getting a rattle, or clanking in my SL320, somewhere behind me whenever I go over one of those short stone, or rubber speed bumps at very slow speed.
The rear subframe was recently overhauled, with new mountings, links & bushes and the only thing that I can see is odd is that there is the best part of 1/4" of play between the washers between the bolts and the underside of the subframe, where the mountings are fitted.
The washers are quite loose and sloppy on the shank of the bolts, so I wonder if the noise comes from here, when the subframe is jolted over a bump.
The bolts are tight in the subframe, but I am wondering if the unthreaded section is too long.
I can see that there will be some vertical movement in the bush, but this looks far too much and all wrong to me.
Has anyone come across this before?

 

[Richard Moakes]

I think you have found your problem, I just overhauled my rear subframe on my 500SL, those bolts need to be tight up against a large round or rectangular washer (depending on type of bush used).

There have been supercessions on those parts, that not all the parts counters are aware of. The newer style bushes and clamps require shorter bolts!

Take a look at this thread http://forums.mercedesclub.org.uk/showthread.php?t=50161

 

[SamT]

Thanks Richard,

What I didn't make clear is that I was talking about the front mountings of the rear axle subframe. I think that the issue that you had concerned the rear ones, which appear to be correct on my car.
On mine the fronts look as sloppy as those in pics I've seen of worn-out bushes!
Maybe the issue is the same as you found though, in that the bolts are too long.
It's strange, as I thought that the front mount is only supplied as a kit, with the washer and bolt, so I would have thought that it would be difficult to get that wrong!

 

[Richard Moakes]

Sam,

You are absolutely right, the front bushes are supplied as a kit complete with bolts and washers etc..

Confused now, I was sure I knew what the issue was, I ended up waiting for new clamp plates and bolts to complete the job when I re-assembled my car.

 

[SamT]

Richard,

Maybe they had the same problem as you with the rears, as it looks as if the original fittings were re-used there, but with the new bushes.
Maybe the new bolts for the rear and the front have got mixed and the wrong ones fitted.
The bolts have different part numbers; I wonder which are the longer?

 

[Richard Moakes]

I don't recall which were the longer, however the new bolts were E-Torx, and I know I had to get some new sockets to tighten them up.

Mixed up bolts is plausible, you can remove them one at time in relative safety, so perhaps you could order some new bolts and try them?

One thing is for sure, there is no way the washer holding against the bushing should be loose, thats definitely not right.

 

[SamT]

Thanks for your help Richard,

Bolts in stock at MK, so hopefully winging their way right now!

 

[SamT]

A further thought, the washers appear to have been installed so that they are dished to the outside, the bolt head side. On this side it looks as if the rubber coating may be thicker.
I wonder if they have been fitted the wrong way round?
I haven't been able to find a good picture on the web of how they should look when fitted. Pics are mostly of worn out and rotten ones!
Has anyone got a good shot of how they should look once fitted?

Thanks

 

[SamT]

Result!

Bolts extremely tight to remove. Threads on bolts damaged, I suspect because the old threadlock had not been chased out.
New bolts in fine and torqued up OK. Bushes now properly clamped by stop washers and no rattles or creaks.

I think that the first bolts were so tight, that the fitter couldn't tell they hadn't fully gone home!

To say that I am unimpressed is an understatement!

 

[Richard Moakes]

Pleased to hear of your good result.

Thankfully I chased out all the threadlock on mine, looks like I saved myself some problems.

Now you can go back to enjoying the car, which is always a bonus

 

[television]

Cars are funny things,, I cannot ever re call seeing this fault ever before

 

[kth286]

Cars are funny things,, I cannot ever re call seeing this fault ever before

At the end of the day everything is down to people.

 

[television]

At the end of the day everything is down to people.

Shoot them all problem solved

 

[SamT]

Malcolm,

Yes, I only found it by accident, having taken the rear wheels off to change the ARB rubbers and links as the only other remaining possible source of the rattle, or so I thought. Touched the stop washer with my hand and hey presto a rattle! Other side just the same.

Because I don't want to find myself unexpectedly without wheels, if a job turns out bigger than expected, I use a specialist for the bigger tasks, expecting him to know all the wrinkles. Not so sure now.

 

[television]

Malcolm,

Because I don't want to find myself unexpectedly without wheels, if a job turns out bigger than expected, I use a specialist for the bigger tasks, expecting him to know all the wrinkles. Not so sure now.

On many things,,just commonsense prevails, as it did in this case. Lots of these things are easy to do and check, if you have the tools and a little engineering knowledge. No one servicing the car would notice. It does go to show as in your case when doing anything,,take a look around where you are working.