ABS Modulating front brakes at low speed (fix)

[5litersplorer]

Just before coming to a stop, my 2000 splorer's ABS would start modulating the front brakes. I knew it was the one of the front wheel bearing/speed sensor assemblies.

FYI if you are having this trouble, you can remove the sensor and clean them to fix without having to R/R the whole wheel bearing assembly. They are expensive and I was at the auto parts store looking at a new one for 300 bucks. The bearings on the truck were not noisy so it seemed like such a waste of cash, so I decided to inspect the new one and noticed the speed sensor can be removed on these units.

So, I tore off the wheel, caliper, caliper mount, rotor and backing plate. (About a 20 minute job with a simple jack and hand tools)

I removed the allen head bolt holding the speed sensor in, then using channel lock pliers I GENTLY worked the speed sensor out of the bearing. Be careful as it's plastic. Then i plugged the hole with paper towel. The issue is that corrosion builds up on the mounting surface and causes the sensor to not sit deep enough in the hole giving a false speed reading. Using a razor blade scraper, I cleaned the mounting surface on the bearing, wiped off the speed sensor, applied a little grease to the O-ring and re-installed it.

It was such an easy task I did the other side as a preventative maintenace item.

No more ABS everytime I stop my truck on dry pavement, and I saved a whack of money!

 

[Hoppy]

Awesome!

Thanks for the write up. I will try this to my Ex this weekend. I have completely disabled the system due to this malfunction of the ABS. Being winter time, I would like to have the ABS working, but did not want to spend $800 on new bearings to fix a simple sensor.

Thanks again, I will report back after I try it.

 

[Hoppy]

I took the sensors out of the bearings yesterday evening, and low and behold, the mounting surfaces for the sensors were badly rusted. I chiseled the chunk-rust off and polished the face with a wire wheel on the drill. Greased it well and reassembled everything. Seems like I may have the ABS working again. I will see once we get some slippery road conditions to see if I really did. I couldn't find any slippery surfaces this morning.

 

[MINERALGSVT]

I tried cleaning mine with no luck. Hopefully, this weekend I'm going to replace the hub assembly. Mine pulls to the right, so it should be the left wheel, correct?

Thanks

 

[MINERALGSVT]

Replaced the hub assy.... problem solved.

http://www.explorerforum.com/forums//showthread.php?t=165429

 

[5litersplorer]

I tried cleaning mine with no luck. Hopefully, this weekend I'm going to replace the hub assembly. Mine pulls to the right, so it should be the left wheel, correct?

Thanks

Yup, should be the drivers side if the vehicle pulls to the right, as it's modulating the left wheel. You may want to try again, and pay very close attention to the flat mounting surface of the hub that the sensor sits on. Rust builds up here, and you may have to chisel it off with a small hammer and chisel or flat screwdriver, but this maintenance trick should work. Also make sure the end of the sensor has been wiped clean too.

Correct tolerances are important for these sensors to work properly. Mine had a lot of rust on the drivers side, and minimal on the pass side.

 

[Hoppy]

Thanks 5litresplorer,

This fix worked for me. It was the front sensors. I finally got my ABS hooked up again and it works like a charm so far.

I wonder if this should become a sticky? I am sure that this is a common problem that many people encounter.

 

[5litersplorer]

Glad this worked for you, mine is working perfectly. No false modulations. GM has a service bulletin on their full size trucks for this problem. The key is to make sure you get all the rust knocked off the flat surface that the sensor sits on so that the sensor depth is correct. This may require a die grinder and a cookie, or a simple hammer and flat chisel.

I think it should be a sticky considering the cost of the hub assemblies. How do I make it a sticky?

 

[Hoppy]

I used a chisel and hammer, and then a wire wheel on the end of my drill.

Only problem was, I almost lost the paper towel in the sensor hole. I would probably try something different if recommending it to someone else.

Compressed air would have been handy as well to clear out the debris from the screw hole.

Once cleaned, I greased the mounting surface and reinstalled the sensor.

Quite an easy job I must say and it saved me over $800 for new bearings.

A moderator I beleive is the only authority to make this a sticky. I'm not sure how to contact one though.

 

[markcoronado]

I know this is an old thread but i just want to say thanks for the info.
I have a 95 EB and your fix worked great and saved me a lot of cash.
Thanks again

 

[kelgeo]

Ya this is a old thread but this is a common problem that mechanics like to say is a abs computer problem that will cost alot. I wrote about this in another thread since I'm trying to solve this problem, I'm glad I'm not alone. who knew that doing a brake or bearing job would cause so much of a head ache. I will put in a new speed sensor and clean the area.