Clunk on drivers suspension

[SteveX]

Hi Chaps,

Some assistance would be appreciated as this is driving me insane.

My car had zero noises and drove fine, fast forward to MOT time he said the bottom two arms had play on the driver side.

So I replaced the two arms and when it was back together I have a clunk over bumps at speed from the drivers strut?

I removed the strut and found some play, if I press down on the top mount and let go / bounce it, it makes a small clunk. The top mount was also split, so I replaced top mounts on both sides.

The clunk is still there?

I've disconnected the ARB that didn't help so it isn't coming from there and removed the shock / strut again.

With the new top mount on if I bounce on the top of the mount with my weight it makes a clunk when the shock reaches it's maximum travel?

The lock nut for the strut was screwed down tight and the same as the other side which is fine. I really have no idea?

It was fine before I removed like I said and then the clunk started. It's almost like there is too much travel, but if I tighten the lock nut down any more it will jam the bearing and rubber top mount so I don't want to do that and damage it.

Any ideas?

Many thanks.

 

[LostKiwi]

What car is it?

 

[SteveX]

w209 clk55 convertible

 

[SteveX]

So I took it all off again, compressed the spring, and engaged the lock nut as far down the thread as it would go until it stopped. Then re-fitted the strut and went for a drive - still knocking on the front.

I took it down the road, went over sleeping police men > no noise.

I got out a block of wood on the drive, about 2" thick, went over it with each front wheel in turn separate > no noise or clunk. Turned the wheels went over it with each wheel back and forth with the steering turned > no noise.

Go down the road over mild bumps > clacking on the drives side.

I'm sick of taking the ****** thing apart and off.

Any other suggestions? I just can't see what could be making the noise.

BOTH arms on this side are new, the top cap and mount / bearing are new. The drop link was disconnected so I could try with and without it active.

The only thing I haven't change is the track rod end, but it just sounds like it's up the top of the shock near the top cap :/

There's no oil on the shock, no marks, all seems good there too.

Ugh...

Might be time to throw it at a garage, and throw even more money away. Already spent £400 on a spring, two top mounts and two arms.

 

[LostKiwi]

Are you sure it's not the strut? W212s seem to have a weakness which results in clunking as you describe which is cured with a new strut.

 

[SteveX]

I just can't understand why the strut would fail though, between me taking it off and just putting it back on in the garage?

The last thing to try on the strut is to take it off (again, sigh) then remove the cap and spring, then test the shock extension is 20mm < less I guess.

 

[SteveX]

Update, removed again, strut is fine. The noise I get is only if I disconnect the roll bar, and allow the hub to drop right down thus pulling the shock to it's maximum travel limit, I think this is normal, since it will never be this extended in real life. With the ARB attached, jacking up the strut and allowing it to drop to it's full extension then = no noise. Also no noise through travel on the shock when all attached, so I think we are all good there.

Checked outer tie rod today on driver and passenger side > all good.

Removed boot on inner tie rod, checked ball joint and steering rack / teeth > all good. Did repack it with fresh grease while I was there

Swapped the front arm again > still have a noise

Swapped the rear arm with the old arm > still have a noise

Put the roof down, windows up, went slow, face on dsahboard > no noise...

The noise does seem high up, I am actually starting to think it may just be the roof! Being a convertible it does have its squeaks and rattles, I am starting to wonder if I am just being paranoid since fitting all the new bits and listening out for the slightest noise!

#confused.

Also went all around passenger side again, and every bolt, checked for play, everything is solid.

 

[SteveX]

I haven't driven the car much, but it seems to of got worse!

I've checked all over and the only thing I can see is that the top mounts sit about 1mm above their resting plate. So the threaded top that has two notches in and a plate bolted on top, side above the actual rubber ring on mounting point.

Mercedes was going to take a week to order the top mounts from germany so I went with Corteco mounts from ECP which they assured were 'OE quality'.

Now I am starting to thing that the top mounts are out of spec. If these plates are supposed to rest on the rubber rings in the engine bay they do not, they sit about 1mm above it, and the mounts are fully torqued down to the lowest point on the shaft of the shocks. This would likely be why I can't get any noise when going over bumps - it will be when lifting off over bumps as the plate hits the rubber mount / bump stop. I can't think of any way to stop this, other than changing them.

I am thinking of ordering two from mercedes, then taking these back once the new ones are on, but I don't want to order two new ones and go through all this hassle if I am barking up the wrong tree...

 

[LostKiwi]

That plate looks about right to me (don't have a 203 to compare to but the plate on my 129 has a similar gap).
I'm not so sure about that tab to the right of the picture - that seems to be holding the mount high on the body. Are you sure its fitted correctly? None of the pictures I've found on the web seem to show that tab.

 

[towat]

Had a similar problem changed everything including top mount, still clunked over speed bumps, eventually gave in and changed arb bushes, had discounted these as already replaced 6 months earlier, but fixed problem hopefully won't reoccur in another 6 months.

I was starting to wonder whether it was suspension at all and was checking inside engine bay for anything loose such as washer bottle etc.

 

[SteveX]

Thanks for the replies chaps.

All useful info and thoughts, but I now know where it is coming from (or at least the location).

So here is what I ended up doing, not satisfied with the ECP parts, I removed everything again, I got genuine mercedes parts ordered which I have now fitted, this includes new top mounts again and spring mounts, retaining washers and top plates. I also had the shocks inspected > they are perfect.

So here is what I have done:

> Checked ARB bushes > fine as fitted thicker ARB and pollybushes last year, removed to check though and regreased
> Checked steering rack and tie rods, re-packed steering spindle with fresh grease
> Replaced top mounts with OE
> Replaced springs
> Replaced retaining locking nuts on shocks
> Replaces top retaining plates and nuts
> Replaced front arms top and bottom

And guess what? The noise was still there, in fact it's got worse...

So I went out for a drive with my father, I was at my wits end, he told me to put the roof down as he thought it was coming from near the windscreen and guess what? Zero clonking...

We tried roof up and down several times with me sitting in the passenger seat and back of the car with my ear all over the place, it is 100% coming from where the roof latches to the front!

So my taking the front of the car apart 10 times was not required...

The only thing perhaps I can think of, is that with all the new parts that the front is tightened up considerably, and with any flexing of the chassis or variation in camber of the road and bumps from left to right wheel transmit more to the chassis now (whereas before the worn rubbers and joints had slack). At least that is my only explanation other than it just being a coincidence.

It wasn't all for nothing though, at least I have genuine Mercedes quality parts all over the front end now, and the steering is considerably lighter now (I had thought the steering on my car was getting very heavy, the new top mounts are a vast improvement). There was also a distinct difference between the CORTECO top mounts and Mercedes, even though CORTECO seem to have a good rep and are manufactured (so say) in Germany. The differences are that the mounting rubber inside the seating collar of the cap has a different consistency (much more flexible and thinner) and is also a different shape, meaning the spring mounts at a slightly different height and angle. Also the top rubber bearing / bush does NOT lock on to the top mount like the OE one does. Add to that the rubber weather skirt is much more flexible and flimsy, as is the bush. So it was definitely worth the change. Both top mounts, collars, skirts, and plates cost me a mere £135 (with 10% discount) at Mercedes and only took two days to come through in the end > the same price for the top mounts from ECP.

I sometimes buy parts from ECP for convenience and availability if they state OE quality and spec, but I will be very cautious in future.

Anyhow, so now I need to work out why the hell my roof is clonking as the car goes over bumps and dips in the road. The front is solid, it's latched well, not lose at all and I can not replicate the noise or move it. I regressed all of the rubber and seals this spring, and I can't see any adjustment at the front, it sits flush and perfect. Something is making that noise there though and it has to be sorted as it's driving me mad.


Thanks,


Steve

 

[SteveX]

Oh, also, the locking rings are of questionable quality (the OE ones), they have been replaced and Mercedes have been told NOT to use the old ones. They are very easy to chew up with the small tool when torqued up.

As a result, the previous locking nuts and collars were around two threads higher than they should have been on the shock.

The new ones seem to be more solid, and torqued down no problem. They are literally £2 odd each, so well worth changing if anything is thinking of changing a top mount, as are the retaining plates at the top (again only about £5 each so well worth doing).

 

[AMGeed]

Glad you eventually found the reason behind the clunking noise. Pain in backside stripping out the suspension but at least that is all OEM and working properly now.
Cars! Got to hate them sometimes.