ABS rear wheel speed sensors- bad??

[groptus]

I was getting a lot of pulsing as I slowed down, and then a 1-2 second brake application (sounds like a thumping) which would release just before the van stopped. I borrowed an OBD-II for ABS which showed my right rear wheel speed sensor was reading 12-14 mph faster than the other three sensors. I am thinking this is causing a malfunction in the ABS? I cleaned both rear sensors, and the brakes still act the same way. I ended up pulling the ABS fuse for now- do I need to replace the wheel speed sensors, or could it be something else??? -98 3.8L GL, 70000 mi.

[yotermanic]

I wouldn't hesitiate to replace the sensor, they tend to go out on the rear. If you want to save some money you might remove the sensor from the backing plate and reinstall it, sometimes they unseat. But usually you end up putting a sensor in.

[cougarman]

Originally Posted by groptus

I was getting a lot of pulsing as I slowed down, and then a 1-2 second brake application (sounds like a thumping) which would release just before the van stopped. I borrowed an OBD-II for ABS which showed my right rear wheel speed sensor was reading 12-14 mph faster than the other three sensors. I am thinking this is causing a malfunction in the ABS? I cleaned both rear sensors, and the brakes still act the same way. I ended up pulling the ABS fuse for now- do I need to replace the wheel speed sensors, or could it be something else??? -98 3.8L GL, 70000 mi.

The rear wheel sensors ussually need cleaning and " carefull adjustment"
1st clean all the crap and filings from the sensors, the carefully tap the sensor bracket behind the backing plate with a hammer until the sensors are just missing the ring,,,, make sure you don't crash the sensor into the ring. I have had to do this to my 97 about every 2-3 years, I guess heat and rust create too big of an air gap

Good luck

[DRW1000]

Originally Posted by cougarman

The rear wheel sensors ussually need cleaning and " carefull adjustment"
1st clean all the crap and filings from the sensors, the carefully tap the sensor bracket behind the backing plate with a hammer until the sensors are just missing the ring,,,, make sure you don't crash the sensor into the ring. I have had to do this to my 97 about every 2-3 years, I guess heat and rust create too big of an air gap

Good luck

Cougarman. I wonder if you could expand on your adjustment technique.

For example do you tap the sensor braket from the back of the brake plate? Is the sensor out when you do this? Do you have the drum off to monitor? ....

Any more info would be helpful.

Thanks

[12Ounce]

Are the sensors exchangeable, left-to-right, just for testing purposes?

[BCMedic]

They may be exchangeable just for testing but all 4 on my van have different part numbers.
Alldata for my 97 has a ton of information on the ABS and traction control systems, testing ect.

I would replace that sensor but I'll dig through it and post any relevant info if needed.

[cougarman]

Originally Posted by DRW1000

Cougarman. I wonder if you could expand on your adjustment technique.

For example do you tap the sensor braket from the back of the brake plate? Is the sensor out when you do this? Do you have the drum off to monitor? ....

Any more info would be helpful.

Thanks

The following repair is for a abs coming on when almost at a stop, say the last few feet of the stop. The abs light is not usually on. I have done this to a 1996 & 1997 w/star.

I learned this from a Ford tech at a dealer about 4 years ago.. He informed me that there is no published spec from Ford for the actual "air gap".
Remove the drums, carefully clean the filings off the sensor.Inspect the exciter ring and sensor for any obvious damage like cracks. Visually inspect the gap between the sensor and the exciter ring. It should be approx 15-20 thou.. gap (although I have never measured it and there is no spec published). Line up the sensor so it's between 2 of the ribs of the exciter ring to reduce the risk of damage to ring and sensor when performing the next step . Then from the back of the backing plate tap the sensor bracket so it bends slightly which will bring the sensor closer to the exciter ring. once your happy with the gap, do the same on the other rear wheel, trying to keep the gaps of each sensor approx the same. After your done slowly turn the rear hubs while inspecting the sensor and exciter ring to make sure they won't collide with each other. Since the drums are already off, clean and adjust the rear brakes. reinstall the drums, adust up the rear shoes. install wheels and go for a road test.

I hope this description will help you out. If not let me know.