Lower Control Arm Bushing Replacement?
 

The lower control arm bushings on my 82 380sl are shot. So I'd like to replace them.

If I compress the spring and unfasten the shocks and connecting links, will removing the bushing bolts allow me to lower the control arm enough to remove the bushings -- or does the ball joint not have enough play to allow that?

Thanks in advance for the help.

I wouldn’t advise such a procedure if you value your life!!. Suggest to obtain a threaded rod ¾” 500mm length, nuts & washers and 100X100X6mm steel plate to rest on top the subframe spring housing to secure the spring from flying off the perche should something go wrong!!. I would not rely just on the shock or jack to hold the spring in place.. Just under $20 for the kit. It would allow you to lower the arm to replace the bushings.

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Thanks very much for the fast and very informative reply, Deltacom.

I suppose I should have mentioned that I intended to rent and use the appropriate Klann spring compressor to compress the spring. But your system appears to be just as good, and less costly. So I'll go that way.

I did notice, however, that some people used a similar system, but they welded the top nut on to the plate. But, after looking at yours, I was wondering if that was really necessary?

In any event, as you've evidently done this job before, let me also ask you whether it was hard to get the bushings out of the control arm after you lowered it; ie.can you just pull them out, or do you have to do something else?

Also, assuming that everything goes as expected, how long would you say it should take to replace the lower bushings on each side.

Thanks again in advance for the help.

Hi Bill,

The spring compressor cannot be used with the subframe on the car as it would not go through the bottom opening of the arm. I used the compressor with the frame removed and from the top opening as per pics.

Quickest way I found to remove the arm bushes is to cut with a hacksaw the outer part of the bushes (both sides) flush with the arm and use a 10M threaded rod 20” long with long nuts and washers (see pics) passing the rod through both arms and using just a spanner to pull the other bushes through. I think you can replace the bushes within an hour per side.



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Correct me if I'm wrong, but doesn't Klann make a compressor that will fit up through the hole in the LCA?


When you say " use a spanner to pull the other bushes through", do you literally mean pull the rod through, or do you mean use the spanner to turn the nut which will pull the rod through by shortening the distance between one end and the other?

Bill

Hi Bill,

Yes, but not for 107 model LCA (see video). There is a compressor that would go through the LCA opening but is not made by Klann, it is MB tool (see pic). In any event, the way you wish to remove the bushes with the arm attached to the steering knuckle/hub and the springs in place (feasible) you do not want to compress the spring but just to secure it.

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Klann Compressor

Yes, of course, you use the spanner to turn the long nut (long nut because the amount of torque you need to pull those bushes from the arm is quite substantial and an ordinary nut would strip the threads). I used a ratchet socket at the end of the rod secured with a nut just the size to go through the hole on the arm to push the bushes out. Then you reverse the action and direction of the rod with the tightening nut on the side you just removed the bushes.

Edited: I would like to add that you would make this operation easier for you if you remove the springs using the previously mentioned rod and plate but with a 600mm long rod (the car needs to be on stands quite high to allow the rod through the LCA). Once the rod is in place with the nuts just tight without compressing the spring, supported with a jack under the LCA, then you remove the eccentric bolts and gently lower the jack a bit at a time, release a turn or so the lower nut followed by lowering the jack until the spring is loose. (Installation is the reverse). With the spring removed you can turn the LCA outwards to work on the bushes without being under the car.

This has been mentioned before in threads on this forum and The Other Forum: It is recommended to use ACME threaded rod to do this. This is a trapezoidal thread designed to withstand higher loads. Trapezoidal thread forms - Wikipedia, the free encyclopedia

Just think, Those 2 springs are designed to suspend the entire weight of the front end of the car under all forseeable conditions, and knowing the German penchant for overengineering things, plus a sizable safety margin. This translates into one of those springs under compression storing One Hell Of A Lot(tm) of kinetic energy. If one of those things breaks loose, Bad Things will happen. :eek: Use the strongest types of components to make your compressor, and overengineer it some yourself. Don't mess around and do things by half measures, the limbs (or life) you save could be your own.

Just a suggestion,
Scott

I have personally done this 3 times.

You don't need a spring compressor....in fact the MB manual has 2 options.....one using a cradle and one using a compressor. I used the cradle option. Without the cradle!

You simply need to get the front end in the air, floor jack under the control arm, remove stab links and shock nuts and then remove the eccentric bolts. lower the table and the spring falls out with absolutely no tension.

Subframe Gusset Reinforcement and Bushing Replacement - Benzworld.org - Mercedes-Benz Discussion Forum

Spring Replacement: Lowering The Front End - Benzworld.org - Mercedes-Benz Discussion Forum


Good write up with many pics.

That was an excellent job you did there Nobby. Congratulations on the gussets welding!!.

That is true Nobby, for the simple reason that MB do not call it “spring compressor”. It calls this tool “spring tensioner” Part No. 107589033100 (on the pic above) an is used when the special cradle for the LCA is not available (the case of home DIY mechanics) to secure the spring and prevent potential slippage when a jack trolley is used (the purpose of the rod and plate mentioned above) using the spindle Part No. 10758903110 with a cup that sits on the upper opening of the subframe. The spring tensioner is also used when the rubber mount for the spring needs replacing to compress the spring to remove/install a new rubber without the need to remove the spring.


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107589033100 2K OUCH!!!
I had purchased a used Klann (clone) compressor and found out the hard way that it won't work from the bottom. This was several years ago. Later found threads that stated it would not work. Hind sight and all that. It sits in it's pretty case out in the barn.

You are right, Delta. I glazed right over that. I apologize and will edit my previous post.

I still stand by my personal experience, though.

And yes...a second person is required to control the jack while the other person guides the control arm on re-installation.

I am, in general, a safe worky. I did not feel unsafe what so ever doing it this way.

Very informative thread, guys. Thanks :)

I'm just wondering now, although the LCA can be lowered without a spring compressor, would using the compressor to relieve some of the tension on the spring eliminate the need for a second person by making it easier to raise and hold the LCA in position while you insert the bolts?

Also, does changing the bushings make much of a difference in the ride or handling? In my case, the front-most bushing on the left side is torn, but the others seem to be intact. However, there's no noticeable clunking. So, I'm wondering if it's even worth the effort to replace that one or all of them at this point?

Well, mileage, mostly, affects those bushings. Lowers take more of a beating than uppers for whatever reason.

I replaced them because of the gusset welding and because "I was already in there".
If you wanted to remove all traces of front end looseness then I would say put 'em on the list.

You'll never be criticized for replacing 30 year old parts.

MB sells the "kit"...comes with new eccentric bolts and the bushings.

I believe that they recommend minimum new eccentric bolt nuts. But if the bushings are shot then the bolts might show wear as well.

The second person is only needed to guide the LCA back into position while the other person keeps control of the jack. Removal can be a one man job.

Old, thread, but the instructions are timeless. However, Nobby never did say what this strap was for ?

Also, I can see how using a jack to lower the LCA without securing the spring wouldn't be unsafe, because it's relieving the spring's tension. OTOH, it seems to me that raising the jack and having to move it around to get the bushings to line up with the holes in the sub-frame could cause the spring to pop, particularly out of its relatively shallow depression in the LCA. So, would it not make some sense to, say, wrap a chain or rope around the spring to prevent it from doing that when its being compressed ?