230sl rear brakes lose adjustment

[Bruce Tews]

I have tried many times to adjust the rear drum brakes on a friend's 230SL.  The brake linings are fine.  I must say, I think the design of these rear brakes is suspect, however, I must think that Mercedes must have thought the design to be OK.  So, I am suspicious of the friction disks that keep the brake adjustment intact for at least a few hundred miles, and should be at least a few thousand miles.

The rear brakes on this 230SL, after adjustment (and please, with all due respect, I have the owner's manual which is clear on how to adjust the rear brakes and have followed it well) do not hold the adjustment.  After less than 100 miles, the brake pedal goes more than halfway down.

The master cylinder is new, all brake hoses replaced, new fluid, but the rear brakes continue to lose their adjustment.  The brake pedal is fine after the rear brakes are adjusted.  Again, I think the friction disks which allow the adjustment to remain intact for awhile are shot.  Where can I get the parts?
Thanks to all!
Bruce Tews

[jameshoward]

Have you absolutely definitely got the brake parts installed correctly? It is the easiest thing in the world to get wrong and very hard indeed to spot. For example, there's no guarantee that putting them on in the same way they were when you went to take them off is correct. Again, I've made this mistake. We had the car running but couldn't get the brakes to work properly before we realised we'd installed the components correctly.

I have the same car and my brakes are superb. (Bit fiddly to set up, but they are perfect now).

[Bruce Tews]

Thanks for the info.  I never removed the rear shoes to check the parts.  The car was purchased by my friend a few years ago, and it was supposedly maintained by a Mercedes mechanic.  I will take the brakes off the driver's side to check things out, but I am afraid I would not know what the correct sequence of part installation is.  Any pictures or description?

[al_lieffring]

the brakes with the friction discs are from a pontoon era car. the 230sl rear drum brakes have a excentric cam to manually adjust them by two 19 mm hex heads outside on the backing plate. you may have an axle out of an ealry 220sb. the brakes with the friction discs were called "Mystery Brakes" because you never kenw for sure if they would work or not.

[ja17]

Hello,

Al is correct on this. Some ponton sedans, 190SLs, 300 SLs and the early finback sedans used this arrangement. They worked quite well when all parts were in the correct place. I usually sandblast the side of the shoes to give the friction pads for the adjusters a little more bite. Any grease or oil on the side of the brake shoes can render the self adjusters useless. You can test the self adjusters by prying the shoes outward, when released they should retract just a slight bit then hold. If they are not working properly they will move in too far causing excessive brake pedal  travel. I see how you cannot find information on the self adjusting brakes, since they were never used on the W113 cars! Go to the 190SL Groupe website for a lot of information on these self adjusting brakes. The friction pads are also the same as what you are working with, except on a 190SL the  self-adjusters were used on all four wheel. 

Joe Alexander
Blacklick, Ohio