w124 rear suspension

[d215yq]

As per my previous posts my car has been increasingly unstable to drive particularly with high winds so had a garage check out the steerign and perform a wheel alignment which didnt seem to solve the problem.

I therefore presume it's play in the rear suspension as its the rear that tended to shift and feel very unstable at 60mph +, particularly over lumpy roads/in crosswinds.

Yesterday i did a long journey fully laden and the car started bottoming out and had practically no rear suspension over even slight bumps. Looking at it today the rear sits very low on one side, so I presume that means a spring has gone (a quick look and i coudlnt see it was obviously broken but understand its not always obvious if it breaks at one end).

I have no problem taking it to a garage to get the spring fixed but I'm just interested to hear if anything else could cause these symptoms. Also, as its been sittign at correct height for last 5 months but still unstable to drive I'm guessing its not just the spring thats the only issue here, or could a warn spring that had not yet broken cause the wandering and instability?

I only ask because in my experience some garages have been a bit lazy and if they see a broken spring they'll presume thats caused everythign and then it'll probably come back with the same wandering issue when i ideally want the whole thing sorted in one go.

Thanks,
Ben

 

[Richard Moakes]

It sounds like you need two new rear springs, however these were unlikely to have been the cause of your instability.

I would get your mechanic to check the various control arms that secure the hub to the subframe. When these are worn the car will behave exactly as you describe, it will wander in windy conditions and particularly on rough roads. I would also get him to check the subframe to chassis bushes as well, these are also likely to be worn and need replacement.

Sorting all of this out could be a bit expensive, but a 1996 W124 Coupe is definitely worth it.

 

[television]

Hi Ben,, a broken spring could be whats wrong here,,your instability could be the front bushes in the rear sub frame, this is a well known fault and many post on this, this year.

MB make a special tool for removing them.

You should have a chat with Hertfordshire merx

 

[d215yq]

Thanks as ever for quick posts guys, glad you agree it is likely to be two problems not one as I guess it is more cost effective to get the whole thing done in one go.

I'll see what my local mechanic says as letchworth is a bit of a trek from me, but will contact hertofdhsire merx if the mechanic doesnt seem to understand the car as you describe.

When u say a bit expensive are we talkign megabucks? I do like the coupe but I was planning on switching to a 190e cosworth some time soon so if we're talking 600-700+ might be better just to just put that towards a cossie instead, particularly as 124 coupe prices arent strong at the moment (not high mileage 220s in 'average' condition anyway!)

 

[Richard Moakes]

Springs will probably be in the region of £50 each, £30 if you don't mind non-genuine ones. The control arms overhaul kits are around £50 each, but they won't all need replacing, and the bushes don't cost all that much at all.

I would estimate you will be looking in the region of £250 worth of parts and I wouldn't know about the labour, as I am generally DIY and avoid paying anyone to work on my cars.

 

[d215yq]

What bushes are these?

After paying £30 for the mechanic to tell me theres nothing wrong and the tyre pressures of 2.4 bar instead of 2.0 bar are probably causing the problems, decided to have a look myself.

Not an expert on suspension so unsure what i was looking for with loose control arms but nothing obvious was loose or hanging off. However I did find that one bush had completely perished and another had some play in it (the red bits in the attached diagram. Apologies its a bit poor but it is meant to be the view from just behind the rear axle looking forwards down the car. Are these bushes what is referred to before as the "subframe to chassis bushes" and therefore could these be the cause of the banging/instablity/car not always sitting fully level at rear?

Thanks as ever, Ben

 

[d215yq]

now with picture attached (hopefully)

sorry, not got to grips with the adding images.

 

[Richard Moakes]

The bushes you have marked in red are the differential mounting bushes, they will cause banging noises on takeup of drive etc.... so could well be one of your problems.

Not sure your mechanic understands W124 rear suspension, tire pressures will have an effect, but are unlikely to be the only cause of the instability.

I will attach a diagram showing subframe bushes in a few mins....

 

[Richard Moakes]

Items in red are of interest, items in green are what you identified.

 

[Richard Moakes]

This diagram shows the links which may well have wear in the bushes at the ends.

 

[d215yq]

An update

Many thanks for those diagrams Richard, I've now had a look at all the bushes/links and also got (another) mechanic to look at them while I watched and apart from the differential bushes I highlighted everything is tight with no movement at all.

The car also seems to somewhat miraculously not sit low on one corner any more. My only guess is that i originally checked after the car had been fully laden for a 300 mile drive so maybe it hadn't quite 'readjusted' to being unladen again? Also the mechanic said the springs were not broken, nor excessively rusty, though they are original so maybe couldnt cope when the car was fully laden but are OK when it isnt.

I put a new rear tyre on as it was close to the mimimum tread, let some air out the tyres and had it retracked (again) and now (unladen at least) it soaks up bumps a lot better and is more stable over rough surfaces.

Still some wandering at high speed, particularly in the wind but I don't see much else that can be done. Only thing I can think of is if warn front ball joints could cause the car to wander yet still appear to be fully tight when stationary? There's no other symptoms of warn ball joints and both mechanics said they were fine, though not sure how thoroughly they checked!

sorry to bang on and i'm sure i'm being overly fussy but I just know that it didn't behave like this when i first bought it and its annoying when you know something isn't quite right!

 

[Bolide]

It's not always easy to find wear - you really need to know what you're looking for. Just because you can't see the wear doesn't mean it's not there

The usual suspects for wandering are the rear toe control arms (about £15 each), worn steering boxes, worn steering idler and worn steering parts in general. Broken up rear subframe bushes will have an effect as well

Have a look at

http://www.detali.ru/cat/oem_mb2.as...GM=717.413&CT=F&cat=15T&SID=35&SGR=075&SGN=04

The rear suspension arms are available in a repair kit - parts #104, #83, #59 & #122. I think it's #104 that controls toe-in and when this one wears it allows the car to steer from the rear. Check the parts with your local Mercedes parts man

Nick Froome
www.w124.co.uk