95 WS abs problems

[caddy57]

Hi all I have a 95 3.8 w/89000 that is having abs problems. It all started when the weather warmed up. The abs unit would come on every time I used the brakes. Then it started coming on while driving down the road.It would run for about 2-3 min and shut off with the abs light coming on. I had my guy check all brakes and rotors etc. and all is fine. Finally pulled the fuse under the hood.I've checked posts, but haven't found anything about the unit coming on while driving. Anyone have any ideas?
Thanks
steve

[wiswind]

You might try cleaing the ABS sensor actuator gears, one located at each wheel.

http://rides.webshots.com/photo/2030...11220610romxdY
Shows the location of the front wheel speed sensor and the "exciter" ring (looks like a gear).

http://rides.webshots.com/photo/1361...11220610aXnisj
Rear drum brake system.....showing sensor location.....you can see the "exciter" gear to the right of the "+" that marks the sensor location.

As each "tooth" of the gear passes the sensor....it causes a electrical signal in the sensor, which the computer sees.
Wheel speed is determined by the number of "pulses" from each sensor.

It is not unusual for the sensor to be bumped and be too far from the gear like exciter ring......
Also....just plain dirt and grim.....brake pad dust....etc to gum up the teeth of the exciter ring.....
So a good spraying with brake cleaner.....and a check to make sure that the sensor is close (but not touching) the exciter ring teeth.....as well as a look to verify that the sensor wire is intact at each wheel.....would be a good first step.

It sounds like the sensors are thinking that a wheel is not moving as fast as the others........just 1 sensor will cause that.
The ABS system compares the wheel speeds with each other......1 wheel moving slower than the others is what it is looking for.



Also, sounds silly....but verify that the brake fluid level in the master cylinder is at the top side of the FULL line.
Even slightly low can trip the low fluid sensor......which can light BOTH the BRAKE light and the ABS light.

[caddy57]

Originally Posted by wiswind

You might try cleaing the ABS sensor actuator gears, one located at each wheel.

http://rides.webshots.com/photo/2030...11220610romxdY
Shows the location of the front wheel speed sensor and the "exciter" ring (looks like a gear).

http://rides.webshots.com/photo/1361...11220610aXnisj
Rear drum brake system.....showing sensor location.....you can see the "exciter" gear to the right of the "+" that marks the sensor location.

As each "tooth" of the gear passes the sensor....it causes a electrical signal in the sensor, which the computer sees.
Wheel speed is determined by the number of "pulses" from each sensor.

It is not unusual for the sensor to be bumped and be too far from the gear like exciter ring......
Also....just plain dirt and grim.....brake pad dust....etc to gum up the teeth of the exciter ring.....
So a good spraying with brake cleaner.....and a check to make sure that the sensor is close (but not touching) the exciter ring teeth.....as well as a look to verify that the sensor wire is intact at each wheel.....would be a good first step.

It sounds like the sensors are thinking that a wheel is not moving as fast as the others........just 1 sensor will cause that.
The ABS system compares the wheel speeds with each other......1 wheel moving slower than the others is what it is looking for.



Also, sounds silly....but verify that the brake fluid level in the master cylinder is at the top side of the FULL line.
Even slightly low can trip the low fluid sensor......which can light BOTH the BRAKE light and the ABS light.

Thanks for the reply
I'll check out the sensors and rings once it warms up. Back down to single digits again. I have noticed that my brakes are alot quicker with the abs disabled thought this was odd.
Steve

[wiswind]

From what I understand, someone correct me if I am wrong......With the ABS light on.....the ABS unit will not work....
Your brakes will work just like the old fashion....non-ABS system....no pulsing when a wheel locks up.
That is.....if there is not something wrong with the basic braking system....which the wheel sensors are not a part of.

The reason that the ABS is disabled when the ABS light is lit is that it is telling you that it sees a problem......it cannot rely on the data that it is seeing, so it shuts down.
ABS does NOT apply the brakes.....it momentarily turns the braking pressure OFF to a wheel that it sees as locked up......
It ends up pulsing the brakes ON and OFF to a wheel that it sees as locked up.....

[caddy57]

Just an update: Today was warm [50 F] so I decided to check the van out. I was reading more of the postings and all said to check the the fluid. So I decided that I should check this out first. The level was about 1/8 inch low. I filled up the res. and put the fuse back in. Took it for a drive and no problems. Who would have thought. Went and told my mechanic, and he said I was crazy. He took it for a drive and came back and told me, in over 30 years working on cars he had never seen something like this happen before.Never to old to learn.
Steve

[caddy57]

Originally Posted by wiswind

From what I understand, someone correct me if I am wrong......With the ABS light on.....the ABS unit will not work....
Your brakes will work just like the old fashion....non-ABS system....no pulsing when a wheel locks up.
That is.....if there is not something wrong with the basic braking system....which the wheel sensors are not a part of.

The reason that the ABS is disabled when the ABS light is lit is that it is telling you that it sees a problem......it cannot rely on the data that it is seeing, so it shuts down.
ABS does NOT apply the brakes.....it momentarily turns the braking pressure OFF to a wheel that it sees as locked up......
It ends up pulsing the brakes ON and OFF to a wheel that it sees as locked up.....

Just an update: Today was warm [50 F] so I decided to check the van out. I was reading more of the postings and all said to check the the fluid. So I decided that I should check this out first. The level was about 1/8 inch low. I filled up the res. and put the fuse back in. Took it for a drive and no problems. Who would have thought. Went and told my mechanic, and he said I was crazy. He took it for a drive and came back and told me, in over 30 years working on cars he had never seen something like this happen before.Never to old to learn.
Steve