ABS Light on :(

[105547111]

Hi,

I have a 528i, I bought it and have been repairing / restoring it.

Everyting is fine except the ABS light is on.

When the ignition is turned on the light is on.
As soon as the engine starts the light goes off.

If I drive real slow (10km/h) light stays off. If I press the pedal I can feel the ABS pulsing the pedal.

If I go faster (about 20) the light goes on and stays on.

The rear rotor sensor on one side was rusted, I wire brushed and rust treated it.

I checked the front and all appears fine there. Cleaned the sensors and rotors also.

As the front are plug in, I checked and saw the same resistance on both. I cant find where the rear sensors are plugged (I am guessing inside the cars interior somewhere, as they are one peice from sensor to inside of floor (from underneath.

I checked and I have 12v on the large relay (all the time) and I got an ingition 12v on the small relay.

Any suggestions where I can look and check?

Thanks!

[lwebb12]

what year is it?

[SoonerE39]

Originally posted by lwebb12@Sep 19 2003, 08:21 AM
what year is it?

And mileage?

[EXtech]

what year is the car?? Any prior work been done ??

[105547111]

Guys,

Okay sorry its an E28, 1985. Its just about to go to 200,000 Km. Everything else I have been able to fix, but the ABS fault is proving to be difficult

As for prior work, the guy I bought it from is a good friend, he was actually going to wreck the car So I got it from him and have been fixing it. He got it from the origional owner.

All I can say is the mechanic who did work for my friend is a butcher at best (he is in the wrong trade).

The reason my friend was going to scrap it, was his wife overheated it, so I expected at least to fix the head.

After I got it I drove it was not too bad but VERY smokey when you restarted it after you left it for 20 minutes, so I knew the seals/guides were no good. Apart from that it drove well and smooth and had good power. Compression tested and only 140 PSI but all cylinders even.

I pulled the head off and got it fixed, just seals and guides. However I noticed bad rust in a few cylinders. Oh well only a few more bolts and the engines out. Then I found the gearbox (4 speed auto) was held on with two bolts!!! and the starter with one!

When I stripped the pistons and crank no surpise the crank was thrusting bad (due to missing gear box bolts!).

Anyway I got another set of pistons, bored it, decked the block and head and its all going again! Apart from motor most faults been unplugged or broken things.

The ABS I feel its a sensor issue, as at low speed (very low) I can feel it working. I have read up and know rusted rotors (for ABS sensor) can cause problems, but this seems mainly at 120ks or more. Surely unless there is nothing left by rust it would work at up to 100ks. The rust is not that bad. There was some pitting, but the teeth are still there!!

Thanks!

[Disco E30]

ghead

I am having exactly the same trouble with an 1989 E30 325. If I find out what it is I will let you know!

[sammajeed52]

Having the same problem on my 86 535i ...

[dykaar]

Sheesh, kidz. One problem is that the "gear" on the hub has filled up with crap over the years and now the signal is too small at low speeds and the ABS brain thinks you've locked a wheel.

I cleaned the gear with a teeny-weeny ball mill (from a Dremel tool) in a cordless drill.

There is a bosch tool that plugs into the cable in the glovebox and identify the low sensor.

Alternatively, you can use a voltmeter that has a Max-hold setting and drive to a set speed, say 10 mph, and record the voltage for each sensor.

The second issue is that the sensors get squeezed by corrosion in the hole in the hub and the pickup is forced further away from the gear. I used a pipe cleaning (metal) brush to clean the hole, and file to remove the raised bits of the sensor on the gear side to get the pickup closer to the gear. Itsa bitch on the e28 because the metal splashguard doesn't come off with the hub in place.

I bought a couple used sensors before I started in case I snapped something, which I did. The corrosion in the sensor hole was so bad on one that the sensor came out in pieces.

Now if I could only bleed the damn clutch...