Anti-lock brake system on the fritz - (85' W126) Anyway to disconnect the ABS system?
 

My 85' 380SE obviously has a bad wheel sensor(s) on the ABS braking system. Upon depressing the brakes the first time after I pull forward, it feels like the ABS system is activating (and I can hear a groaning under the hood) and then ABS will activate again when depressing the brakes for a couple of times (without the noise this time) after I press them after that and then everything is normal - SOMETIMES. Sometimes I can still feel them operating at certain stops and all of this occurs when the warning lamp is off.

Sometimes after it has did this a few times, the "ANTI-LOCK" warning lamp will illuminate and the brakes work as normal. I am assuming that when the light illuminates that the anti-lock has de-activated itself, hence the ABS activation going away. Sometimes this light will come on within a few minutes, sometimes it takes longer and then sometimes it never comes on.

I am wondering if there is anything that may be damaged continued driving like this? Is there anyway to deactivate the ABS system, just so the normal braking system works? I am guessing there is a fuse for it, or a connection at the ABS unit? I suppose I could check my owners manual to see what fuse works it and what all else is on that circuit.

I would really like to get it repaired, but I am stingy and not ready to spend out $$$ for new wheel sensors. I know- I should not even own a Mercedes if I am stingy with money right? :D

Thanks in advance!

Either disconnect the computer OR either of the relays at the HYDRAULIC unit..under the black plastic cover.

No, you're not alone in the stingy department...
 

...when it comes to ABS repair, that is. I have similar problems, and no intention of throwing money at it either. Since I only drive the car in summer/fall, never in winter, and seldom in rain, working ABS isn't a big priority.
I believe that the system goes into fail-safe mode when there is a problem detected, like a faulty sensor. So you'll always have brakes (providing of course that the hydraulics and everything else non-ABS is up to snuff), but there is that annoying dash light.
Taking out the bulb tells the system there is a problem, so that's not a good idea, or so I've read here. I tried black tape on the outside, but that looked bad, so I tried it on the inside, but it didn't block the light at night, and heat from the bulb will melt tape applied directly. My solution was to remove the bulb and holder and push it to the back of the cluster under the dash.
So I have working ABS about 50% of the time, more or less, judging by the pedal feel, which is odd when it is acting up (kind of a scrunching sound and fee), and I just keep on motoring...:)

Its funny how stingy people are so willing to manipulate the law. It is a federal crime to disable a safety system on an automobile.

You are right about whats happening. Whenever the light is on the system has recognized a fault and disabled the system. From your symptoms you are also probably right that it is a wheel speed sensor. The car does a self check at 10kph. Above that speed faults are registered. Below the system reacts to improper sensor signals with activations.

Wheel speed sensors increase the amplitude of their signals with speed and often a poor one becomes sufficient by the test speed. In a case like yours it seems marginal and sometimes its accepted and sometimes not.

A simple test with the proper equipment identifies the culprit. Otherwise replace both front sensors. It seems to me the right one goes most often, but that could be just a Florida thingy :)

Thanks for the replies.

I can understand why disconnecting an airbag should be a "crime", but I think they should draw the line on ABS brakes.

Look at all of the cars that did not have ABS brakes years ago. Even in 1985, it was optional on most Mercedes cars, so whats the difference? I am sure that there are even some brand new cars today where ABS is still optional- or at least there were some up until a couple of years ago. Besides, if the system is not working properly, whats the difference? I am a very safety conciseness person and normally I would not even suggest to myself about disconnecting the system, but that much $$$ for a wheel sensor is ludicrous.

But I do know what you are talking about.

Thanks Don for that information. Mine also has that "scrunching" sound when I apply the brakes on the first start-up and the pedal will make funny movements when I am depressing the brake, even without the noise at times.

Luckily, the light really does not bother me. It accompanies the "BRAKE" warning light where my ER brake pedal is too low. :D

We have tried that tape trick before on other cars in the past (check engine lights), but it leaves a messy glue mess on the cluster covers, so i'll not go that route.

I do not think my instrument cluster has ever been removed on my car and I am afraid to go tamper with it now. Knowing my luck, I would damage something. :rolleyes: :D

<<<It seems to me the right one goes most often, but that could be just a Florida thingy
>>
I notice the same thingy on the rear control arm outter bushing.. they always seem to b the right one .. My thoughts are more road rash on that side of RHD vehicles...probably the opposite condition in England...
Look at the front of the rocker panels on some and you also see the paint has worn off the front leading edge behind the front tire on the right side on some , while the left is fine...

??????????

I realiize this is an old thread, but I'm now having additional braking issues and am trying to eliminate the ABS as the source. I'm getting a shuddering or vibration like driving over a corrugated pavement, mostly when the brakes are applied at high speeds, like 60MPH +, and not all the time or necessarily at high speed, as it does this sometime at 40MPH or so too.
It's not a warped rotor, as the vibration is not felt at the pedal. I pulled both front calipers and the rotors spin true, one pad is worn more than the other on the driver side (suggesting a sticking piston on the other pad maybe, leaving the worn one to do the work?), and all pistons can be easily retracted with a C clamp.
Since I've had a previously noted problem with the ABS (see earlier post this thread), I'm thinking that the vibration is caused by the system activating erratically or from a bad sensor signal(s), so I'd like to test to see if braking is normal with the ABS bypassed.
My questions:
- Would pulling the 2 relays from the control unit change the braking system to standard non-ABS hydraulics, and are there any negatives to doing this?
- What is the difference removing only one of the relays, as opposed to both, or is there no difference?

Don't disconnect anything yet!!
 

I have a similiar problem (scrunching brakes at slow speed) with my 93 300 TE. It is worse in the winter and better in the summer. My mechanic believes this is because newer brake pads are made out of new materials (including pieces of metal) which wear differently and have different friction coefficients; this confuses the computer. His advice was to brake very hard from 50-60 mph down to zero every so often to smooth out the brake pads. Using this technique we have been able to manage (not eliminate) this problem.
Regards,
Steve

Wow, this is an old thread, I cannot believe it has been over 10 years since I originally posted this, but thought I would just share here instead of a new thread.

That '85 380SE is long gone. I never did figure out the ABS issue on that, but I later purchased a '88 300SEL in October of 2008, which we actually still own. It is now my moms car as I gave it to her around 2012.

The ABS brakes were fine until my dad changed the front brake pads around 2010, then it started doing the same thing as my 380SE. When going down the drive going slow, the ABS would activate and kick the pedal up then during driving the light would eventually come on. It has went through another set of pads since then and wearing down the pads never changed anything. I am guessing he damaged a connector or something when replacing the pads. It is going to their mechanic soon for some front-end work so I may have him check the ABS connectors as well if he can and perhaps clean them and see if that helps. I think 6 years is long enough to be dealing with this. ;)

i can't believe that one guy saying folks are stingy.Folk buying used vehicles can't afford fixing some stuff.dummys,need abs.