300E ABS engaging in reverse
 

Hello all,

I've noticed lately that while operating in reverse at slow speeds,(pulling out of my driveway) my brake pedal will give once or twice, as if the ABS system is kicking in. It happens with my foot just slightly applying brake pressure :confused:

Any clue what could be causing this? It is starting to become quite annoying.

Thanks in advance!

It is a defective or fouled front sensor. Remove and clean them or replace them both or take it to someone with a Bosch LED tester.

I bat 1000 picking them out in my parking lot switching back and forth watching the analog representation of the speed signal the tester gives. It is better than watching with a scope, but that works well also.

1.000 huh? Not a bad batting %.

Thanks a lot Steve, I'll take a look at the sensors.

Where exactly are these ABS sensors located? On the caliper? Will following the ABS line from ABS module lead me to it?

Thanks again,

Follow the wires. At the wheel you will have brake pad wear sensors and speed sensors. The speed sensor wiring is heavier.

Hey Paul,

My 300TE did exactly the same thing. The sensor wires run from the caliper into the firewall on either side of the car where they meet the wires from the abs unit in the form of a plug (next to the battery on passenger side, next to the fuse box on drivers side).

In the interm while waiting for your new sensors, simply unplugging them will cause the brakes to act normally (sans abs effect). Also, I have read it is not always the sensors themselves, but too little voltage running to them from the abs unit.

Good Luck!
Klaus

Unless you have traction control there may be just one sensor at the front of the diff instead of on the rear wheels.

Thanks for the replies
 

Hopefully I won't have to replace these because they aren't cheap. I'll scrub 'em down real good and see if it helps.

Thanks again,:D

I get this same thing, but both forward and reverse. Is this the same problem, most likely?

300E ABS engaging in reverse
 

I have owned two MB's where this Brake Pedal "Kicking" occured and I was assured that it was normal.

One of these I still own, a 190E, and every morning, going backwards or forwards, it "Kicks" a few times. My 300E was the same.

This is only the ABS pressure buildup priming the system.
It has done this from the day I bought it new nearly 20 years ago.

Mind you on my 2001 E320 CDi this does not happen ever.

Mike

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I also get a groaning noise and something like a 1 second- moan/pulse when I first put the car in gear and begin to move (foward or reverse). It will not happen again until the car is turned off and re-started. I was told this was the ABS computer testing itself. I liked this explanation because it meant everything was ok. Now I am worried. Something new every week... Mike

I know what you mean, my '92 pulses once after every startup. I have been told it is a self check.

My '86 does it all this time at crawling slow speeds, sometimes for almost ten feet. My question remains: Is this an ABS sensor problem if it happens in both foraward and reverse?

Normal? Thats a good question. The control unit has mapped responses for every situation? Infinite?

A while ago I wrote an article about BMW transmissions: http://www.continentalimports.com/ser_ic100076.html In it there are scope patterns for the wheel speed signals that the trans recieves. It uses them for purposes described. There is also a scope pattern of the four sensors while the car is in a full lock turn at a couple mph in our parking lot.

If you view the difference in wheel speeds that are possible during normal activity and try to pick faulty locks ups from them there are mistakes made. I can make almost every car do the studder step coming off my alignment lift at a slight angle so I hit the drop off one wheel at a time. The change in acceleration screws with the a braking attempt at the same time.

I believe that the event is improper, its a mistake, if it happened above 6mph it would be recognized by the self diagnostics and the light turned on and the system deactivated. It doesn't cause problems and I'm sure if given the time I could make any car do it. Cars with sensors that are getting bad have this show up as the first sign. Next the light comes on every few drives. I advise you fix it when it bothers you or when the light starts coming on.

Some say defects in safety systems always should be dealt with, this one is a tough call.

Steve, thanks. You have brought me back to earth. Waiting until the light comes on is a good plan. I still may have a look in there and try to clean them -- but will wait until spring!