Weird brake pedal action
 

My 87 560 sl is having some weird brake pedal action. It feels like the ABS system might be engaging during normal braking. The pedal seems to be inconsistent while braking. Had the fronts recently done 2,00 miles ago. Anyone have any ideas?

Describe inconsistant.

When I first got my car sometimes I would get a pull on breaking. One caliper was stuck intermitantly. I had to overhaul the calipers.

Are you getting a pulsing in the pedal that has a frequency proporsional to road speed, That may be warped rotors.

If you are getting a pulsating pedal that is at one frecuency and does not change with road speed that may be an ABS problem.

John Roncallo

first
 

Hi guys - this is my first attempt at this. I recently started having issues with my 89 560SEL - rough idle, black smoke, and an occasional spongy brake pedal - 'pump' it and it returns to the normal feel.

The problem is intermittent, only in the beginning of a driving session. It does not continue after I have hit the pedal a couple of times. The rotors, calipers in the front have just been done, and it does not occur while road driving. I rode the brakes while driving today and it seems to have stopped thep problem.

I also have an ABS brake pulsating right after I start driving the car. It also pulsates sometes when I push the brake in traffic slow speed driving. I had today mechanic clean ABS sensors on front wheels but I still get this pulsating not often but is still there on slow speed braking once in a while. All other brake parts are fine.

The ABS light is not working on instrument at all I only get SRS light on very often and BULB light on when I turn the headlights ON (all the bulbs on car are working fine).


Do I need to get new ABS sensors?

Any idea about the instrument lights?

Thanks for any input on the matter,

Balsa

1986 560sl with 120k.

IMO, these problems with ABS occur because of age, heat, and vibration. The system is very sensitive to minute current variations. Every older MB with ABS that I have owned has had minor glitches like this.

ctaylor738 -
 

So do the ABS Sensors then need to be replaced if they seem to have these glitches?

Thank you.

MARLA

You have a sensor count issue. At slow speeds the sensor output is of lower voltage and thus the pulses can be miss read. This tends to become issues on elder cars as the sensor performance drops, or/and those cars with the following.....

Check for:

1. Rust on toothed ring (the part the sensor detects)
2. Mud on sensors
3. Poor ABS sensor electrical connections - this normally manifests as permanent ABS light.
4. Toothed ring cracks! (In my case)

This is a sore subject with me as the repair cost $1000! See here for more info.

http://www.peachparts.com/shopforum/tech-help/160051-abs-coming-over-sensitive.html

Remove the ABS sensors on the front wheels and clean them. They are magnets and attract the shavings from both the rotor and pad. My 1993 400E did this to me. The sensors looked like chia pets. Once I removed the 'growths' on the sensors, the problem went away and never came back. From that point on, whenever I changed pads, I cleaned the sensors. There was always a little build up but I not like it was when it was causing the pulsating of the pedal. Pulsating was intermittent, by the way.