After almost 20 years of being fitted, I thought it was time to replace the front strut top mount bushes on the Mercedes SL R129. This is part of the SL’s front end refurbishment that is taking place pretty much as I have time to tinker.
The top bush or rubber mount that is fitted between the chassis and the damper/shock absorber leg is a metalastic bonded rubber bushing and as such is susceptible to cracking over time and should be inspected regularly as it is possible for the mount to fail in such a manner that the damper rod can push up into the bonnet/hood with the full weight of the vehicle, if it were to give way completely. £££ !
The video below hopefully documents the simple procedure to replace these bushes, there is no need to remove the road wheel although careful and accurate use of a trolley jack to raise and lower the vehicle (keeping the tyre on the ground at all times to control height) to remove the strut top will be needed. Just make sure that the brake flexible hose to the caliper is not stretched or pulled during this process.
The only other tricky thing is to replace the protective bellows that are attached to the rubber lip on the lower part of the strut top bush, familiarise yourself in how this is fitted before removing the old bush. It will be a fiddle to re-install, and once you develop a technique you will find it quite simple to do. I have even read that some people when replacing the damper / shock absorbers too, fit the gaiter on the bench before installation. This may be worth considering if you are doing a complete suspension job. The best technique I found was to roll back the top lip of the gaiter all round the top (turn it inside out around) then offer up the gaiter. While pushing it up against the mounting lip, roll over the top lip of the gaiter onto the suspension mount – worked a treat!
A straight forward job that can be accomplished with the minimum of tools in a short time.
I found when doing this it was helpful to have a second person( ie. wife) to pull on the tyre/wheel to centralise the shock absorber shaft as you slip the mount and bump stop on as it comes up quickly and strongly when you stop pushing down on it and you don’t have a lot of time to guide it into position.
When doing this I found it useful to jack the front of car completely off the ground and use axle stands on the mounting points under the car by the front jacking points. This allows both wheels to drop the suspension as low as it can go, improving access under the wings. One mount can then be removed without further ado, as the anti roll / sway bar and the other shock mount will prevent the loosened shock mount side of the suspension dropping more than a centimetre (not enough for the strut thread to drop below the strut mount hole.). This all makes: removing the old strut mount, replacing the new strut mount, and the replacement of the bump stop and dust cover (if the latter two are necessary) very easy indeed. CAUTION : with both front wheels jacked off the ground do not attempt to remove both strut mounts at once, as there will then be nothing holding the front suspension assembly in the air! (Unless you support at least one side of the suspension with a jack).
Correction! Me again! In removing my strut mount again, to check whether my Bilstein top mounts were snagging with the OEM strut cap on full compression, as has been suggested (mine ok but a quad nut on top of the damper not a hex, so maybe different damper on the 300-24?) I realised that I must have put my wooden chocks under one/both the suspension arms to stop drop, as without them if you do undo the threaded nut on one side it does drop more than the one centimetre, as I proposed above! (About 7cm, so the thread, inconveniently, drops below the cap top!). Sorry for the misinformation. Still good to raise both wheels off the ground though, as it gives maximum room to remove the strut mount without the anti-roll bar compressing the damper from the opposing wheel, and useful to remove the road wheel too, as easier to manipulate the strut in and out of the top mount.