1987 560sl Rear Brakes are locking
 

Greetings all -

Has anyone experienced rear brakes locking up on a 560sl?
My rear brakes slowly begin to tighten until the car can literally not move an inch. They literally lock.

Any thoughts?

Both rear wheels, or just one of them?

If just one wheel locks up then suspect the rubber brake hose which connects the metal brake lines on the body to the caliper mounted on the wheel. I always change all four rubber brake lines on cars this old - the brakes are the primary safety system on the car.

If both brakes lock up then it's going to be the master cylinder. Rust in the bore of the master cylinder causes the piston which actuates the rear brakes to jam in place, locking on the rear brakes. This is a known failure mode of the master cylinders used on Benzs in that time period - I've experienced it first hand.

Has the brake fluid been changed per the maintenance schedule? Changing the fluid prevents the rust which causes this problem. I bet the fluid is nasty and full of absorbed (or is it adsorbed, I can never remember the difference...) water.

Anyways, either fix is relatively easy and inexpensive. Just don't let a mechanic sell you new calipers, rotors, etc if you don't need them.

- JimY

560sl rear brakes locking
 

Thank you for the info!!!!!!!!!
I just changed the brake fluid yesterday and still the rear brakes are locking. So I think you are correct in changing the master cylinder. I will change out this weekend and hopefully correct the issue.

Thanks Again!!!!!

I had this happen on my 126
 

This occurred with almost devastating consequences. I was driving downhill on a twisty highway in the Santa Cruz mountains. I kept smelling burning brake. I just assumed that it was from all of the cars on this road. I hit the brakes and the pedal went to the floor. I was able to bring the car to a stop (thank god) by riding up on the dirt shoulder. When I got out of the car the brake hoses were on fire! I had the car towed back to the mechanic and basically replaced the whole rear braking system. Apparently the problem was with the parking brake cable sticking (the car sat for three years). At first I thought that I was the most stupid person ever having this happen due to not releasing the parking brake. I checked the lever to find that I did indeed release the parking brake lever and and had just assumed the brakes released as well. Scary and expensive. Check your parking brake system. Good luck.