Help! had a rear brake fire in 1996 500sl - PeachParts Mercedes-Benz Forum

Earlybird · #1 03-05-2009, 10:51 AM

The rear brakes started draging on the freeway the other day and by the time I got off the freeway, the disks were red hot. Now I need to rebuild the calipers and replace the disks, pads and brake lines . Fastlane looks to have good prices but there are 2 types of disks for the rear. One that is for ESP and one without ESP. My question is how do you know you have Electronic Stability program? Did all the 1996 500sl have it? Thanks

jcyuhn · #2 03-05-2009, 01:31 PM

Any idea what caused the brakes to drag? Was it one side or both? On older Benzs that problem was caused by a failure in the master cylinder - BTDT myself. I've not heard of such a failure on a car as recent as yours, but make sure you locate and address the root cause.

- JimY

Two560Two · #3 03-10-2009, 05:41 PM

My best bet would be to call your Local mercedes parts center, give them your VIN and they should be able to decode whether you have ESP or not.

There could be many reason why the brakes could lock up...Maybe due to failed master cylinder, old, contaminated brake fluid, failed calipers, abs module etc...

Earlybird · #4 03-11-2009, 04:24 PM

Yea, it fried the paint off of both sides of the backing plate, turned the brake pads into charcoal and vaporized the caliper piston boots. I can just guess what the piston seals look like. I got out all my little wire brushes and cleaned the backing plates in prep for paint. All the other parts are being replaced including the brake hoses. One thing though, the brake hoses swelling on the inside was not the root cause. I will never know if it's that traction control system unless I test everything else. I'm going to attach a thermal couple to the pads and watch the temp so this does not happen again.

johnathan1 · #5 03-11-2009, 04:26 PM

That kind of heat could destroy the wheel bearings, too...I would make sure everything down there is in good shape after a fire like that... :\

Earlybird · #6 03-30-2009, 12:16 PM

OK, this is the update: I rebuilt the calipers, replaced the pads and rotor and flexable brake lines and the e-brake shoes and springs ($280). I went to bleed the rear brakes with DOT 4 fluid and the pump the pedal process didn't work. I then got out my pressure bleeder and hooked up to the steel lines at the master cylinder. That did work but I got an inch of air in the lines when I disconnected and reconnected to the master. I tried the brake pedal pump method again but again it did not work. I then attached the pressure bleeder to the cap of the master and tried some low pressure bleeding. That didn't work and made a big mess when it leaked. I got to thinking and decided to pull the master. I see no visible problem with it but the piston actuator may need some adjustment. I need to determine if the piston is being allowed to return all the way. If that's OK, I will take the master apart. I am bound and determined to fid the root cause and will update again soon

Two560Two · #7 04-15-2009, 05:20 PM

If the car has some miles on it, just replace the master cylinder for safety reasons and try gravity bleeding all 4 brake lines. Then try pressure bleeding again. If anything you may have to bring it to Mercedes or an independent shop with a scan tool that bleeds the ABS module as well

Earlybird · #8 05-05-2009, 03:39 PM

I replaced the master and before I put the resivoir back on I snapped on my pressure bleeder adapter and let her rip. I passes fluid real well now. I think the root cause was that someone topped off the res with dot 3 insted of dot 4. They are much different formulations and the dot 3 made the rubber in may master cylinder expand and the small shrader valve behind the forward piston was not opening and letting fluid in and out of the compression zone. That is why I got a drag and why the drag got worse with heat (expansion with no release of fluid). The brakes work fine but are a little mushy. Might need to do a bench bleed.