Hurry to your local bookstore and buy a copy of the M/B E-class Onwers Bible for 1986 on. Go to page 78. There is a narrative on the procedure for adjusting the parking brake. Follow the directions and if you are handy with tools, you should be able to cinch them up satisfactorily. I have the same problem, but have just been too busy with family/social committments to get at it. I went to the local library and checked out the Mitchells and Chilton's manuals and they are much the same in their descriptions for the same job. Good hunting!!!
I just had the same problem and fixed it in 10 minutes. Now my parking brake is rock solid.
You need to adjust your rear parking brakes, never adjust the cable. To adjust the brakes take out one of the wheel bolts and find the star adjuster ring, turn it untill the tire no longer rotates freely and then back it off 5-6 clicks. Do this on each rear tire. Good luck.
The star adjuster wheel can be turned with any regular flat-blade screwdriver that will fit through the hole. I forgot to mention that on one side the adjuster has to be turned up, on the other side it's down, but can't remember now which side is up or down. In any case just give it a try with a couple of notches in one direction, if the wheel doesn't lock soon, just go in the opposite direction.
UPDATE: just included a scan of the pages out of one of my books. Should make it easier for you.
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