W126 Rear Control Arm Restoration and Replacement - PeachParts Mercedes-Benz Forum

JamesDean · #1 07-06-2014, 02:04 AM

Hey everyone,

A few months ago I got news from the MB dealer that my 420SEL had a hole in the shock mount area on its driver's rear control arm.

W126 420SEL Left Rear Lower Control Arm - Imgur

I've replaced rear controls arms before. A 300SE and two 300SDs, all passenger sides. This will be the first driver's side.

I found a forum member with an arm for sale and bought it off him. The whole transaction--including shipping--was under $125!!

I got the arm in about 3 months ago but really haven't had time to do much with it until this weekend.

I bought a sand blasting kit and 100 pounds of media. We took the arm and compressor out to the back yard and started blasting.

Progress Pictures are here:
1989 W126 420SEL Rear Control Arm Replacement - Imgur

Final Product:

Its not prefect but its pretty good.

My next step is to wire wheel the whole arm, just for good measure.

At some point in time I am going to have the bushings replace. Not sure if I should do that before the below steps or after... Thoughts?

After that
1) Clean and prep the surface
2) Apply Zinc coating (Eastwood Zinc-Rich Galvanize Aerosol 13 oz)
3) Apply Rust Encapsulator / Protectant
4) Apply durable chassis paint
5) Install!

JamesDean · #2 07-06-2014, 10:45 PM

Update:

Wire wheeled the arm as best I could:

And Hit it with a few coat (one side) of the zinc compound:

Tomorrow I'll flip it and do the other side. Then sand the stuff down a little bit and hit it with the rust encapsulator coating.

560355 · #3 07-06-2014, 11:52 PM

Looks good. I think mine rusted out from inside so I sprayed the new one with cavity type rustproofing. There was an accesshole with plug hidden under the break disc shield.

JamesDean · #4 07-07-2014, 06:57 AM

Quote:

Originally Posted by 560355

Looks good. I think mine rusted out from inside so I sprayed the new one with cavity type rustproofing. There was an accesshole with plug hidden under the break disc shield.

Hmmm I thought about using something like that I've got a can of some internal frame coating stuff but didnt have a nice way to get it inside. Removing that brake shield means removing that hub/bearing thing which I kind of tried to avoid since I dont really have any tools for that.

JamesDean · #5 07-29-2014, 09:27 PM

So here are some pics I took of the current arm. I think its getting worse. I've parked the car until I can get to replace it.

JamesDean · #6 07-29-2014, 09:27 PM

So here are some pics I took of the current arm. I think its getting worse. I've parked the car until I can get to replace it.

JamesDean · #7 08-08-2014, 11:50 PM

I had to outsource the job to my shop. They charged me $450 to put in new bushings, install the arm and swap the springs. Not bad I think.

I had them return me the old parts:

That arm was way worse than I thought:

jake12tech · #8 08-09-2014, 10:12 PM

Why not source a rust free control arm from a southern or western car?

Rust sleeps, but it will come back.

JamesDean · #9 08-09-2014, 10:23 PM

Quote:

Originally Posted by jake12tech

Why not source a rust free control arm from a southern or western car?

Rust sleeps, but it will come back.

I did lol. The arm in the first post is from a South Carolina 300SDL. I re-coated it because it had a few spots where the factory coating got scraped off and bare metal was exposed.