My 1988 560sl pulsates the brake pedal when I pull out of garage in the morning or (abs is being activated)
The brakes , rotars ,hoses , are all new
calipers are rebuilt, fluid is new
when I purchase the car this summer the motor relay for the abs was missing
I replased it and thats when the abs started working . maybe too much
The sensors are all cleand up front and back
I also checked the resistance of each one and they are are within spec.
the abs sometimes comes on at a slow speed stop during the day
but this is happens hardly at all
Is there a problem or thats something normal for that model?
Some of the old threads say this action in reverse is a test, but I can't see how the abs knows when to test itself at least in that year.
Any help would greatly appreciated

Not normal. Our old 190E had the same exact symptoms, and the speed sonesors were "in spec" and I cleaned them. Nothing worked, and then the ABS sensors were replaced and problem solved.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

I may have to go that route.
Did you have to replace the rear one also?
Thanks for the help

actually it is quite a normal problem. this is one of the things that have been a problem throughout the years. it is a little pricey to fix. the pedal pulsates at a low speed? same problem here... at least you know that the ABS is working. not something that has to be fixed and not something that will fail as a result... has been a problem on the 190E all the way up to the S500 but not too sure of the newer ones. this is for the 80's and early 90's models.

Actually, it is not normal ABS operation. It might be a common problem, but that is very different from "normal." The ABS system is not functioning as designed, and eventually the sensors will fail, lighting the ABS light and disabling the system. If you don't mind not having ABS, no problem.

However, if you want to have the system functioning as "normal" than you'll probably have to replace the front wheel speed sensors.

Some people live with the ABS slow speed pulsing and don't care if the ABS fails at some point. If you are one of those (I rarely use ABS, even on black ice) then don't bother spending the bucks to fix the problem.

It's up to you, and no I didn't replace the rear sensor. I would have left them all alone but the buyer for my 190E wanted it fixed.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

I was wondering if there are any other ways to tell which one is bad I hate to change good parts.
But again changing both will end this problem
Its worth it , all the rest of the brakes are new now.

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i said it was a normal problem... maybe i should have spoken your language and described it as a common problem... and the only reason i spoke up on this thread is because i had a long talk with my mechanic about this and i feel he knows much more than you so i will be glad to take his advice. he told me not to worry about the sensors... he never mentioned the abs failing as a result... he explained that it is not a problem with the abs at normal operating speeds but only an issue at low speeds. read your manual... it specifically states in the manual that you might feel violent (and yes they use the word violent) pulses from the brakes during a hard stop... it goes on to explain that that is the abs working and not to worry about it... just in case... it is in the section about the abs brakes in the owners manual.

"(I rarely use ABS, even on black ice)" i cant believe you said this... what do you mean you rarely use ABS... if your car has ABS and you press the brake... you are using ABS! dont think it only works when the wheels start to slip or when the brake is slammed to the floor... it is working everytime you press the brake.

Maybe you don't understand how ABS works, or what it is. IT's not "normal" braking. The ABS system is only used when the tires exceed the threshold of traction and apply and release the brakes in rapid succession in order to keep the wheel from locking.

If the ABS system is working everytime you push the pedal, I'm in serious trouble, since the ABS system in our 190E was disabled by the failure of the speed sensors. If you love your manual, you should read the part about the ABS warning light and the fact that your brakes will work without ABS operation. ABS stands for:
Anti-Lock
Braking
System

The key word is "Anti-Lock."

And while it might seem like semantics, your using the word "normal" sends a message that this how the system is designed, and the flaw is a design fault, not an actual equipment failure. It is an equipment failure and NOT normal. Yes, lots of older MB's have the fault, and it's not critical that it be dealt with, but if you are trying to have the system working as designed, then you will need to make repairs. As to the system NEVER failing to operate at higher speeds, sorry, untrue. If the speed sensors fail completely, you will have no ABS operation, regardless of speed. How do I know? Experience. 800,000km's of MB driving and many repairs on many cars with over 350,000km's. On the 190E I just sold, the ABS was not operating at ANY speed thanks to the complete failure of the front speed sensors. I tried cleaning them (sometimes works) but not in this case.

Why is your mechanic not in a rush to fix this? Not a critical element and it's a fairly expensive repair.

Why don't I use ABS (you can tell, as the pedal pulses during ABS operation) very often? Well, even on ice, I anticipate the low traction and usually don't even come close to threshold braking. Sometimes I do, but not often.

Read up...

http://auto.howstuffworks.com/anti-lock-brake.htm

http://www.autoshop-online.com/auto101/abs.html

http://www.e-z.net/~ts/hybrakes.htm

http://www.abs-education.org/abcs/abctips.htm

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

I agree with what you are saying about the abs
I believe the last owner was too cheap and figured why spend the money and took out the motor relay for the unit.
He had the vechicle for 2 years and did not make as many repairs and maintenance as I did in 3 months
I want to get it back to original with abs working
thanks for the help, I will be ordering the sensors soon
maybe I take a chance and buy one ,go from there.

I had the same problem with my '88 300 sel. ABS would pulse after first brake application after initial start up and ocassionally when coming to a stop at low speeds. Both wheel sensors and differential sensor checked out as within spec. I remember reading somewhere that for some illogical reason the right front sensors seem to fail at a higher rate than the other two. So I replaced the right front sensor first. That was about 4 mos. ago, the problem has not returned.

brgds,

BENZSTER

Thats a good idea
That way yuo cut the cost in half
maybe???
Right side might be the lucky side

"Why don't I use ABS (you can tell, as the pedal pulses during ABS operation) very often? Well, even on ice, I anticipate the low traction and usually don't even come close to threshold braking. Sometimes I do, but not often."

this isnt a question about ABS anymore, this is a testament to your insanity...

you just proved my point... YOU CANNOT SEE BLACK ICE... anyone that tells me that they dont need ABS on ice is in my opinion an idiot that should not be trusted.

im stopping this conversation as i can see that you are not making any sense and i am wasting my time... i never intended to have a chat with you... all i wanted to do was tell the person that started the post about the issues i have had with the problem he is having. if you cannot respect that than you can kiss my a$$.

How on earth did we ever live past 18 before ABS was invented?

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Norm in NJ
Next oil change at 230,000miles

shear luck...

Well, replacing the speed sensors isn't too difficult a job, and I'd offer to walk you through it, but we'll let icetrey the knowledge-god take this one.