My 71 280 sel's left lower control arm broke a few weeks ago. The dealership quoted $6500 to repair it. Half of the cost was parts ($1400 for the control arm). I decided to do it myself. I went to the dealership to pick up the car and talk to the mechanic who looked at it. After talking to him, I decided to rebuild both sides.
My fear was that with age of the car there could be other problems. I would rather be proactive than be reactive.
To do this the list of parts is
2-king pins,
2-knuckle carriers (link pin kit)
2-upper outer control arm bushing kits
2-shock absorbers
1-torsin bar bushing kit
1-used control arm.
When performing this repair job it would time efficient too also replace the following:
2-sub frame mounts
2-engine mounts
2-spring rubber mounts
2-front wheel bearings.
To ensure that rust and/or stress fractures were not present. This involved going down to the bare metal and then painting and clear coating. I used a tabletop buffer with a wire wheel attachment. It was a very dirty process but insures that everything will be up to spec.
***A note on this repair. The photos will switch from one side of the car to another, and also there will be before and after photos mix in. I had forgot take pictures of everything during the process** *
The first set of photos is of the damage to the control arm.
The fracture of the control arm at the bearing bolt bushing.
http://img217.imageshack.us/my.php?image=4damagebc5.jpg
Torsion bar linkage damage
http://img217.imageshack.us/my.php?image=5damagett7.jpg
The shock snapped off when the control arm dropped down.
http://img217.imageshack.us/my.php?image=3damagecs5.jpg
View of the bearing bolt and control arm
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At first, I believed that the failure was due to the bearing bolt and bushing freezing up but upon removal it was fully greased and working properly. The failure was due to the lower knuckle carrier being frozen, which resulted in some distortion in the connection point of the lower outer control arm. This caused undue vibrations in the control arm, which increased as the bearing bolt treads were worn down.
The failure happened when I was traveling at a high speed and coming to a hard stop. The downward pressure fractured the control arm at the bearing bolt connection. I was almost at a complete stop when the cantrol arm broke.
Here is a view of the wear on the threads of the bearing bolt.
http://img217.imageshack.us/my.php?image=8damagepi8.jpg
Put the car on jack stands on both sides and secure the rear wheels (park brake needs to disconnect). Remove the wheels. Remove the shock. Disconnect the park brake cable.
To remove spring, the Mercedes service manual recommends the removal of the bearing bolt. It connects the control arm to the sub frame. This is not a dangerous job as many people have led us to believe. It is not recommended to remove the spring by disconnecting the steering knuckle from the control arm. This is dangerous. Even if the jack fails during the correct removal process the spring cannot and will not fly off and decapitate someone. It is possible the other way.
Place the jack under the spring lift it up until the car starts to come off the support jack.
http://img217.imageshack.us/my.php?image=ajackplacementmg0.jpg
Compress the spring
http://img172.imageshack.us/my.php?image=aacompressspringym4.jpg
Remove the bolts with a 19mm socket and wrench. There are four bolts, which connect the bearing bolt to the sub frame. The bearing bolt is the pivot point for the inner control arm.
http://img217.imageshack.us/my.php?image=bremoveboltsee4.jpg
To remove some of the bolts you may have to hit them with a heavy hammer and push them through with a mandrel.
* note there is a top and bottom to the spring. Also this is a great time to replace the rubber mount on the top of the spring.
http://img217.imageshack.us/my.php?image=cremovespringbx4.jpg
[FONT='Verdana','sans-serif']Once the bolts and nuts are removed (don't forget the washers on the top side of the sub frame they sometimes stick) slowly drop the control arm and remove the spring.[/FONT]http://img217.imageshack.us/my.php?image=dremovespringls4.jpg
Now it time to remove the brake line. The line starts at the top of the wheel well and connects to the back of the knuckle. There are two allen nuts that hold the hard line, which snakes around the knuckle to the caliper. Unscrew the nuts. Then unscrew the nut at the back of the caliper. At this point, the brake fluid begins to flow. Plug the line. I separated the hard line so that I could clean it up.
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Just put the brake line around the connection to get it out of the way.
http://img217.imageshack.us/my.php?image=ebrakelineyk9.jpg
There are two large bolts on the back of the caliper that hold it onto the knuckle. Slide the caliper off.
http://img217.imageshack.us/my.php?image=eeecaliperwi6.jpg
Now take the grease cap off the center of the brake disk. The cap covers the wheel bearings and the nut that holds the wheel on the steering kunckle.
http://img217.imageshack.us/my.php?image=fdiskandwheelbearingswl5.jpg
I will finish posting the repair later on tonight.