I purchased my 1989 420SEL about two years ago and have been busy doing a lot of work to the car to bring it up to my standard. My most recent job was to inspect and replace the W126 parking brake shoes. The parking brake was not holding the car, even after I adjusted it. The Mercedes W126 uses a separate set of drum brake shoes that act on the inside of the brake disc for the parking brake.
Last weekend I started the job, and at first it was pretty easy. The wheel and caliper was off in no time. However, despite removing the small bolt holding the rotor to the hub, it would not come off. Normally a couple of quick whacks with a rubber mallet will break it free and it will easily come off.
I first went back and checked that the parking brake was off, and it was not adjusted too tightly. No issue there. Next I tried WD40, a heat gun and even more enthusiastic whacking with the mallet. Still no joy. I persevered for two days with these methods, with time for the WD40 to soak in, but it still wouldn’t budge.
I called a friend in the MBCNSW who had done a similar job on his 450SLC (the owner of this website). His rotor came off with a few hits with the mallet, but he suggested if that wasn’t working to buy a puller from the auto parts store. He suggested one that looked like it would work from Super Cheap Auto, which is only 10 minutes away.
After a quick trip to purchase the tool, I had the rotor off in two minutes. The long thread centres on the hex head of the hub, and the three hands grip the rotor. Once you start winding the thread, the rotor will pop off like a spring with no warning at all. I’m glad I wasn’t too close to it! Once the rotor was off, I could clearly see the surface rust on the hub and rotor that had been preventing me from removing it.
Once the rotor was removed, I was finally able to get to work removing the W126 parking brake shoes. I used a special tool to remove them, which can be bought from MercedesSource or eBay. I had purchased new parking brake shoes but once I had the old ones off, it was clear that my new shoes did not match. Luckily they had the right shoes in stock and I was able to go and exchange them.
The special tool popped the springs back and allowed me to fit the new shoes fairly easily. I checked the rear rotors and they were still well within specification. Instead of replacing them I cleaned them up with a wire bush on the end of my drill. I was then able to re-fit the rotors and calipers (using Loctite on the caliper bolts). Once the rotor is back in place, the handbrake must be adjusted. There is a small star like adjuster that you can see through one of the bolt holes and adjust using a flat head screwdriver. I first adjusted it so the rotor would not turn, then released three notches.
After that I put the wheels back on and took the car for a test drive.
Author: James Faydherbe De Maudave. James is a member of the Mercedes-Benz Club of NSW and the proud owner of this 1989 420SEL. He is the owner of All Aspects Auto Detail, who specialize in classic Mercedes-Benz vehicles in the Sydney area.
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