Sudden ABS Rear Brake Application
 

Hi all

1987 420SEL.

All of a sudden, the rear brakes applied themselves. No ABS light lit, and only the rears applied. Shut car off, restarted, problem has not reoccured.

But now, every once in a while, the ABS faintly actuates on a slow stop.

What would cause the rears to lock up? How to diagnose? I am guessing the fronts are simply dirty senors or sendor wheel.

I have never had the "locking" brakes, but occasionally I will get the exact same ABS activation when slowing to a stop in my 1988 300SEL (which is the same as your car, only different engine). Its like they are "checking" themselves or something like they do when you first hit 5 mph after you first start out- which that part, I think is normal. :confused:

My old 1985 380SE had the optional ABS brakes and did the same thing, only on that car, the "anti-lock" light would occasionally illuminate when it did this, whereas it does not on my current car.

It is probably the 'brain' going soft in the head. I had the same issue in the SDL. The antilock would kick in at every stop OR the light would come on and you would have no antilock function. You can try cleaning the sensors on the wheel hubs (front) like I did, but that did not help. I just went to the bone yard and picked up a "new" brain from a 560 SEL for $50.00 that is working correctly. They just plug in and you are good to go.

FYI a new computer costs over $2000.00 :eek::eek::eek:

I'll try to find one.

Anybody have a spare they'd like to lend me to try out?

tire size?
 

If the tires are of different sizes, I have found the ABS will be activated when approaching stall speeds.

^^ The tires are identical.
I'm going to swap out the ABS computer with one from one of the 16vs to see if that changes anything this weekend.

It may not be even the abs module.....

It could be circuitry or caused by any modifications you made to the car.

No mods at all. Stock 420 SEL.

I've probably got a box you can try, what is the number on the box in your car?

bump

Part number on the control unit? I might have a "loaner".

Hi Baby
Thanks for the offer. I need to run over to the garage to see what numbers are on my 16vs' units before I bother you with this.

again - THANKS!