Mercedes SL 320 (R129) Steering Idler Arm Bushes – Replacement

In the quest for the best possible drive and ride I had detected a slight amount of front end wander and tram-lining on rutted tarmac.  This was a similar feeling to someone just tugging the steering wheel and forcing the car to steer slightly in an unexpected direction.  This was not a serious situation, just one that I knew shouldn’t be there.


I checked the lower control arm bushes and ball joint on both lower arms, along with all six ball joints in the steering route.  The steering gear checks are easily carried out by simply gripping the ball joint to be tested while an assistant wags the steering wheel left to right.  Any play will be felt in the joint – any perceivable movement between the ball pin and socket, then replace!


Pay special attention to the drag link ball joint ends that links the pitman arm of the steering box to the idler arm.

Look carefully at the top of the steering idler arm pivot while the steering wheel is being swung, any up, down or side to side movement that can be seen with the eye indicates the bushes require replacement.  Bushes in a kit, with a new through bolt and washers are appx. £130 genuine Mercedes or about £40 for URO imported pattern parts.  (Not the best make in the world – but as Lemforder have recently discontinued their offering, the only available option to genuine parts)


On the SL320 (R129) take a 24mm combination spanner and place it over the head of the idler bolt, let the spanner rest against the engine mount.  From underneath, use a breaker bar short extension and 24mm hexagon socket and begin to undo the nut. Once free, exchange the breaker bar for a ratchet and remove the nut and washer. Tap through the long bolt and remove noting the order of the cup shield and spacer washer.

Removing the old bushes is best done first from the engine bay.  Use a piece of steel tube about 75cm long and place it on the steel lip of the lower bush.  Strike the drift/tube from above in the engine bay with a stout hammer and work your way round the bush lip, driving it steadily out of the chassis tube.  When the lower bushing is removed, get underneath and use a shorter tube/drift through the chassis tube to drive out the upper section.


Lubricate the new bushes with red rubber grease. Pop the old through bolt into the new bushing and position it over the chassis tube top, drive it into the tube using your drift/pipe centred over the through bolt head as far as possible.  When the bush is fully home drive the lower section of bushing in from underneath.  As soon as the thread can be seen,  fit the old nut and tighten it up.  This should draw the bush home, reaching the end of the available thread take out the through pin and thread it through the idler arm and retighten until both sections of the bush are completely fitted.  When satisfied replace the old through bolt with the new one, build up the pivot and tighten the nut and bolt fully.

r129 Steering Idler Bush Kit

Mercedes SL 320 (R129) Steering Idler Arm Bush Kit Part Number: 129 460 0019

R129 Exploded steering parts diagram (LHD)

13 thoughts on “Mercedes SL 320 (R129) Steering Idler Arm Bushes – Replacement

  1. Hi do you know anyone in north west london or near Clacton on sea who may replace all of that for a reasonable price please.

    1. Hi Paul,

      Regarding the idler arm bush replacement.

      I am based in the Midlands so my knowledge of mechanics in the London area is non-existent. However I will say if you get the parts from Mercedes yourself, pretty much any mechanic can do this job for you,it is not even difficult for a competent DIY’er so I would expect most anywhere to be able to give you a price. If they quote you for for more than 2 hours labour however go somewhere else!

      All the best

  2. Hi Steve

    Me again,
    Since replacing wheels, tyres, top mounts, LCAs, dampers, steering damper and ARB bushes my 94 SL320, has been driving very nicely. My only complaint is a (very) slight steering wheel vibration. This happens above 40mph and is more related to road surface than speed. A perfectly smooth motorway is fine, but poor tarmac and the vibration appears.

    Now it’s the sort of thing I can live with but I’d rather strive for as close to perfection as possible. Do you think changing the idler arm bushes would help? It seems to be a simple and inexpensive job.

    You mention URO and MB parts, which did you use?

    1. Hi Richard
      I would be checking to ensure correct end float on front hub bearings. If you can feel any play at all when off the ground, they need adjustment!

      The idler bushes are available as a kit from the SL Shop at about 40 gbp, Euro car parts similar. Mercedes genuine parts over counter is about £150. Yer takes your choice!

      Get someone to rock the steering while you watch the idler, if it lifts its worn slightly, if it moves side to side its worn noticably. It could be play in the lower steering column uj, rocking the steering wheel two inches either way while watching will reveal this and also any free play in the steering box. This can be adjusted out if bad but these do have some inherent play by design. In a straight ahead position the steering wheel should rotate no more than an inch snd a half each way of centre, before motion can be detected at wheel/tyre.

      Hope that helps.
      All the best

  3. Well I’ve waggled away, I can’t feel or see any movement. So I’ll just have to find some billiard smooth roads. 😀

    (off to France soon, things always improve there)

    1. Just a thought Richard,
      There is a drag link that joins the steering box pitman arm to the relay arm, this can be identified by the attachment point for the steering damper. Interestingly any wear in these two smaller ball joints can escape the damping action (much like the inner and outer steering ball joints.) These often suffer as they are not easily seen and the boots deteriorate due to engine heat. Its a struggle to get under to see what is going on underneath, but you can get your chief ‘waggler to do their stuff while you grip the joint and feel for any play. Just another thought I had is that if you are testing the steering ball joints in the system in an elevated stance (jacked up to see) they may seem tight, possibly they have only worn in the loaded straight ahead normal travel position. There is a lot of ball joints there and the added play of a little in a few can add up.
      All the best

  4. I checked all the steering joints with the front wheels on ramps, me flat on my back. So straight and loaded.

    Nothing seemed worn. However it’s all 22 yrs old down there, so I may just do everything anyway. Then just the back to tackle.

    Did you use the URO or MB idler arm bushings? Lemforder do the rest.

    1. I used the MB OEM part. Comes complete with that serious through bolt, washers, spacer etc. Expensive but the original had lasted twenty years so good lineage and gauranteed to fit correctly.

      Forgive me if I have already mentioned this but the front wheel alignment at Mercedes is done with a spreader bar that preloads the steering ball joints. Its fitted to the front of the wheels. Adjustment is then carried out to spec. Outside possibility is that you are just on the limit of acceptable toe in and just a tad more would take out the self straightening wanton of the wheels on uneven surfaces. Dunno, worth a mention at least.


  5. Hi Steve

    Thanks, I had a 4 wheel alignment carried out after the suspension work. Front toe is 1.1 on each side total toe 2.2, Everything is “green” so I’m hoping good and within spec.

    I don’t remember them using a spreader bar though.

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