W126 and ABS... did 1984 Model Year receive this? - PeachParts Mercedes-Benz Forum

Hit Man X · #1 12-02-2011, 09:38 PM

I have a bad speed sensor (or main control unit) on my 10/84 build 300SD. Searching has not come up with much so I have a few questions...

Was my SD the first year ABS was standard on the W126 here in the US?

Do I have a speed sensor out back or is my ABS just for the front? I cannot roll around on the ground now as it is raining... but common sense would dictate that I have front and rear ABS.

Does anyone know if speed sensors from the 2nd Gen cars will work on mine? I would prefer not to drop $100/ea to replace them when I know there are many, many good sensors in the parts yards. I seriously doubt my control unit is bad.

Thanks!

LandYaghtLover · #2 12-02-2011, 09:50 PM

All I can say is that "ABS" is all four wheels. Where as the ABS in my 1973 Mark IV was only rear. And called Sure-Track. In fact, anti-lock brakes were nothing new before ABS, but having all four wheels on the system is what makes ABS what is is.

Either way, just look for the large ABS manifold/pump on the driver side by the coil. You will see four lines in and out.

I dont know where the speed sensors are, but in the back they may actually be near the diff and measure the half-shaft instead of the hub itself. Thats how many cars are setup now anyway. Protects the sensors from dust, etc.

I would think they are interchangeable, but the Mark VIII has one year (1998) that are specific to that year. If anything I would say look for a first gen. If there was a change, it was probably with the second generation.

And in my experience brake dust is the number one problem for sensors. Being magnetic, they pick up crap then send false readings. Cleaning sensors fixes 90% of the ABS failures I have seen.

Hit Man X · #3 12-03-2011, 02:01 AM

Well, my F150 only has rear axle ABS and it is single channel so there is just one speed sensor there.

Problem is that my '85 is the last of the 1st Gen cars that came with it in the US... and if they are proprietary to 1st Gen cars I am going to be up creek as I am pretty sure only the only 1st Gen cars here in the US to receive them were in 1985. Most of the gasoline ones are long gone... the 500SEL and 380SE due to our favorite Cash 4 Clunkers program.

I am pretty sure my fronts are clean and it would only make sense the rear is single channel ABS, so in theory the car should have just three sensors. I am pretty sure the cars with ASD? or ASR received four channel (four sensor) ABS.

E150GT · #4 12-03-2011, 07:23 PM

I think there are more first gen cars with ABS than 1985, but they are hard to find. I know I have seen some earlier models with it. I dont know about the interchangeability of them as my SD does not have it. I remember there being only three sensors. Cleaning seems like a good idea. I remember a plastic bag got caught up in my rear end and cut the sensor wiring on the diff of the 420 once. I used butt splices to crimp it back together and it worked. They are pretty reliable even though they are exposed to everything.

compu_85 · #5 12-03-2011, 07:36 PM

IIRC ABS was optional starting the 1984 model year. Memory seats and an airbag were optional for 85.

The ABS system on the Gen2 cars is the same.

The only cars with 4 speed sensors are the gassers with ASR. Even the diesels with ASD just have a single sensor on the diff. (it just compared rear axle speed to front wheel speed)

-J

Hit Man X · #6 12-06-2011, 03:20 AM

My '80 W126 has ABS, too bad it was stolen.

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