1995 sl320 R129 New Owner- Front Suspension Knock...

[The Dude]

Morning all, trust life is treating you kindly.

Since owning my SL (2months) have been fiddling with latest changes (pics to follow)
New fuses to replace old slightly tarnished one's
Installation of Ctek battery maintenance check unit in boot which shows battery charge status and allows easy plug in for charging so no more removing rear battery cover

Now after replacing steering damper and front roll bar bushes I still get knocking from the front suspension...garage checked with me present and tightened steering box quarter turn but could find no other wear in suspension components?
I have ordered lemforder control arms ( local mb dealer wanted nearly £600 for a pair!) And hope this will fix this well known problem...advise please and will be ordering an idler bush kit from the SL Shop today...
Thanks Giles

 

[RichardF]

Theres not a lot to the front suspension. The ball joints on the control arms hide wear well, difficult to check when under tension. Good chance they need doing if original.

Otherwise, shocks and top-mounts. (If the shocks aren't torqued up properly it can cause knocking)

Lets us know what difference the idler arm bushes make.

 

[The Dude]

...thanks Richard.

I purchased the idler kit from Ebay as unavailable from my local MB dealer ? Anyways the seller KMS confirmed it was the correct part so local indy bullied the old bushes out and when the new ones were offered up they were smaller ! Micrometer confirmed nearly 1mm so old ones were greased up and re-installed ! Now KMS are being difficult vis a vis a refund!

& please be kind enough to tell me how to set the shocks up as this is helpful advise? And the knocking sound is a heavy one on take up and low speed manaouvering thus inclined towards ball joints? What are the symptons of worn top mounts which in my case look to be good, in that there is no pershishing to the rubbers top or underneath?
Best wishes...

 

[WDB124066]

"Knock" does sound like ball joints - which are on the control arms.

Worn top mounts will change your castor and camber angle more than allowed for in the design when on the move. In bad cases the cup tears from the rubber and introduces itself to your bonnet - although from memory there is a small stop pressed into the mount parts to try and prevent this, the stops are rubber coated so you would not expect a noise. Have a close look at the center and outer part of the bush and see if there is a gap between the two "lippie" bits - it will become clear when you see them...

 

[RichardF]

The top mounts tend to crack and perish. If yours look okay they're probably ok.

The front shocks are easy to do, but a rookie mistake is to not torque up the top nut properly. Unless it's been off I'd expect it to be fine, but might be worth giving it a tweak.

 

[RichardF]

Just another thought, part of a major service is to check the torque on the steering box mounting bolts. (they bolt through the drivers side wheel arch)

 

[WDB124066]

I really don't feel comfortable contradicting you Richard but those top mounts are very difficult if not impossible to see in car if they are in good condition.
My advice is that they last about 100 000 miles before they need replacing as a consumable i.e. as a matter of course. If you are doing the rest of the suspension it makes a lot of sense to do these as well. It's a bit like having a top end hi-fi with cheap speakers.

 

[RichardF]

I replaced mine, cracking & crazing around the rubber was easily visible. I don't think they were about to collapse but it gave me peace of mind.
I've been working my way through the front suspension so it's all new now. I didn't discover (neither did the MOT guys) worn ball joints until I had the shocks off.


Plenty of R129 steering/suspension stuff on this site


http://www.mercedes.gen.in/mercedes-sl-r129-front-strut-top-mount-replacement-video/

 

[The Dude]

...really helpful advise and gratefully rec'd...car booked in this week for the new arms to be fitted...really hoping for quiet front suspension !

Best wishes to all.Giles

 

[WDB124066]

Not only should you have quiet suspension you should also have quite a "pointy" car. The old drag link steering can be faily direct when everything is set up properly.

After adjustment of the box and the idler arm it is quite important to have the ball point position of the steering links checked and adjusted as reqd, otherwise the toe out on turns may not be set correctly meaning excessive outside tyre shoulder wear.

 

[The Dude]

...Thanks for adding to this thread. I have had the car adjusted on a Hunter machine and the front was 'made good' however whilst the rear was a little out they were not keen to bully the adjustment bolts for fear of breakage although they indicated that the alignment was not too are out to cause any issues...

I am hoping that the new lower lemforder arms will resolve the clunking issue as I have read forum threads revealing tales of people struggling to identify the issue and having to replace just about all of the front suspension components!

My car has 55k on it so one would hope that this low mileage means less wear to all mechanical components? Having said that she is 21 !

 

[WDB124066]

You're welcome Dude, that what this site's about.
Toe out on turns is hardly ever measured by alignment techs, often it is not a straightforward measurement for them to take with the machinery they use, so it gets ignored. Taking play out of steering boxs and idler arms can change the BPP and you would not know this because it isn't measured either.
You may need to contact MBUK to find out who has a BPP check tool. Most Dealerships have thrown them out.

You can have your ball joints checked for play by people who know how to do this on a 129, they are in tension and there is a specific way to check that people who check ball joints often have no idea about. Get it to a specialist if you want to know it is ball joint wear that is causing the clunk there will be play but only if it is tested correctly.

If there is no play the clunk may be from other sources like ARB mounts where they join the chassis - often they crack on the 124 at least - not sure about the 129's.

If you are looking at new non Genuine LCA's make sure the shock absorbing suspension bushes are assembled in the correct orientation. Most are not; on Febi LCA's for example, not sure about Lemforder. Take a photo and post before the are fitted...

 

[Vlad]

We had a 129 in recently with a clunk from the front and looked at all the usual suspects, including the top mounts which looked fine when you just looked at them, but with somebody in the car and turning the steering, the rubber top mounts opened up. Once replaced, the clunk was gone

 

[JCW1]

If there is no play the clunk may be from other sources like ARB mounts where they join the chassis - often they crack on the 124 at least - not sure about the 129's.

This was certainly the case on my R129, droplink fractured through work hardening at the point it was bolted to the chassis. Got to be worth a look.

 

[The Dude]

Well...both lower control arms changed by garage (horrible pig of a job!) and amazingly the original MB ball joints had no play at all! The bushes whilst showing their age were tight...

So...has the clanking gone? Nope...thus far; have changed the arb bushes,idler bush,steering damper and now lca's...tis all tighter but remains noisy like something is
loose ?

Paying a mobile tech to take a look tomorrow as nothing obvious is apparent? Gearbox mount , steered box? Wheel bearing? Who knows but bloody annoying mystery!

So if anyone wants to make me an offer for two original M B arms feel free...Nearly£600 from my local dealer!

All the best.

 

[rusty55]

Hi I had stealing damper changed. And drop links but finally the knocking went when new disks,pads and holders were changed Driven 4000 miles since now knocking free
My local Indy in Swindon new all about the cause on r129. Did the job just fine he said some dimensions of disk pads cause the rattle in its holder often after driving over uneven roads or gully

 

[The Dude]

...well rather than being defeated I went back into the garage contorted my body under the car and banged around a bit and noticed that the cross members knocked when hit! Next I removed the outer bolts and drove the block and guess what? No knocking! Unbelievable as the clunking noise sounded like a component was about to fall off...
Moral of the story...replace everything until you locate the actual fault ☺

All quiet on the western front...

 

[WDB124066]

Pictures....? Helps others.

 

[WDB124066]

You're welcome Dude, that what this site's about.


You can have your ball joints checked for play by people who know how to do this on a 129, they are in tension and there is a specific way to check that people who check ball joints often have no idea about. Get it to a specialist if you want to know it is ball joint wear that is causing the clunk there will be play but only if it is tested correctly.

If there is no play the clunk may be from other sources like ARB mounts where they join the chassis - often they crack on the 124 at least - not sure about the 129's.

.

Did they choose to ignore this, or not test them properly...?

 

[The Dude]

...I tested them and couldn't find play,they tested them and couldn't find play...however because the rest of the front end was nice and tight and given what I have read about ball joints on this model and the fact that the bushes and joints were 21 years old concluded changing them even if it didn't resolve the issue couldn't hurt?
What is interesting is how the x brace underneath (4 bolts which I undid with a 45 Torx on a breaker bar) if not correctly tightened can cause such a significant clonking noise! I think the braces must bang against the little rubber bushes sitting between the brace and body of the car and the sound reverberates through the car with the sound coming from around your knee area when driving.My recommendation is rather than just tighten the bolts,remove them and reinstall...also given the braces rather light construction I wonder what contribution they actually make and wonder if they can be removed without issue?
What do those of you much wiser than me think?
Enjoy your bank holiday...