'85 500SL (Euro) ABS Braking Problem

[sublettd]

Scanned several hundred messages looking for someone with the following problem. Alas...

When driving above 60 MPH and I hit the brakes, the car veers sharply to the right and repeats with every pump till below about 60 MPH. (Feels like what I would imagine riding on a surfboard is be like.) Below 60 MPH brakes act normal, with a slight pull to the left. Have replaced pads, fluid, drag link, tie-rod ends, but to no avail.

When I purchased the car the ABS light was on..."been that way since I had it..." Brakes worked fine till my mechanic "cleaned up a sensor". Since then... My thinking is the previous owner might have known of the problem and found a way to defeat it.

Curious what the problem might be, but also whether I really need the ABS for a good functioning braking system and whether I ought to ask my mechanic to "restore the problem light"???

Thanks,

Don

[stevebfl]

If your light is on then the ABS is off!

Your problem sounds like a normal brake or suspension problem. You should have it looked at.

[sublettd]

Originally posted by stevebfl
If your light is on then the ABS is off!

Your problem sounds like a normal brake or suspension problem. You should have it looked at.

Steve,

Thanks for the response.

Perhaps I wasn't clear. The ABS light is now off and my problem seemed to start about the time he cleaned up one of the sensors.

I'm thinking it's a problem with the ABS computer that was somehow bypassed previously and that is why it was bypassed. I can assure you from the way it acts that it's not a 'normal' brake problem.

FYI, I have two other MB's--an '82 300D (Euro) w/272,000 miles and an '82 300TD w/130,000. Just happened to come across this one with 90,000 miles and the body in sterling condition. Have spent about $2,500.00 on repairs to get it up to speed. Once I get this problem resolved I'll breathe a bit easier.

Thanks again.

Don

[stevebfl]

If you think that it is an ABS function then pull the controller. Then there will be no ABS and the light will be on. Do this for test purposes and see if the symptoms are the same.

I have fixed hundreds of ABS problems, none of them sounded remotely like your problem. It would take a coordinated effort to do what your symptoms suggest.

[sublettd]

Steve,

This is a weird one I have to admit.

Going to drop the car off to my mechanic tomorrow. He's going to drive it home so he can get it out on the road.

I'll suggest he disconnect the controller after he sees what it's doing.

I'll let you know what comes of it so you can file it away for future reference.

Got another one if you're interested.

Temperature spikes to the red line after it warms up and then drops back to about 90C. However, it fluctuates with stop and go driving. Have replaced the thermostat and sensor on the thermostat housing. Problem still exists.

Have seen this discussed in another forum here, but nobody appeared to have a satisfactory answer to what is causing it. My mechanic suggested a bad ground might be the source of the problem. What do you think?

Thanks Again,

Don

[Kebowers]

There is a small air bleed pasage and hose to the radiator on the top of the thermostat housing. If that is plugged, or the air bleed hole in the thermostat is plugged (check valve sticking? non factory top thermo housing?), the air will be trapped below the thermostat (insulating it from the coolant) and cause the 'spike' on thermostat opening and erratic temperature swings. You have to get all the air out.

[sublettd]

Kebowers,

That makes a lot of sense. Will check it out tomorrow when I pick the card up from my mechanic. Will let you know if that fixes the problem. Thanks much!

Don

[sublettd]

Update on my problem(s)--

Brake problem is looking more like the calipers are causing it. Starting to pull a bit left now, so it's definitely not ABS--according to my mechanic. FYI, he drove the car home last night and the problem got his attention. He drives his own race car and said he'd never experienced anything quite like that. (I believe he thought I was on crack until he experienced it first hand. ha!)

Temperature gauge--found the hose(s), but haven't had time to see if one is clogged. Mentioned that to my mechanic too, and he said, "Oh, we know about that and bled all the air after changing the coolant." I'll check it to see if there is a clog or air in the system this weekend.

Thanks again for the suggestions!

Don

[sublettd]

Finally got my '85 500SL braking problem solved. Replaced the calipers, pads, drag links, tie rod ends, and master cylinder. Not sure it was any single thing that was causing the problem but, according to my mechanic, the lack of camber in the wheels makes the car super sensitive to nuances in the road and any play/slack that might be induced from one of the above. Also went ahead and replaced the steering box due to the fact it had been adjusted all the way out.

May have done more than what was required but all the parts appeared to be in need of replacement. At any rate, I'm comfortable that I now have a good braking system.

Don