Brake are "wonky"

[jailfood]

Guys and Gals.

2002 TB with 204k. Pads are good. Calipers aren't sticking. I am not loosing fluid.

But.... when I go to stop the antilock brakes pulsate, even on dry pavement. I am thinking bad wheel bearing. The ABS lite has come on a couple of times when first starting the truck but goes off within a couple of minutes. The brake lite did come on once for about 5 minutes. This problem has been getting progressively worse in the last month.

So questions are.

Do we all agree on the wheel bearing ? - they have about 70k on them, dang I drive alot.

Is there any way to tell which one ? There are no noises coming from either side.

I know if I take it to my mechanic he can read the ABS codes but will it tell him which wheel bearing ?

Why can't autozone provide a tech II for cripes sakes. ?

Would pulling the ABS fuse stop this ? I know I would have to pump brakes if I start to slide, gee back to the way I learned to drive.

Thanks for the thoughts.

 

[dmanns67]

When both of my wheels bearings went bad, I heard a humming/slight grinding sound around 35mph, but never had an issue with the ABS.

It might be worth getting the codes checked prior to throwing parts at the vehicle.

You could check for the wheel bearing by jacking up each tire, one at a time, off the ground, grab each side of the tire and push/pull to see if there is any play.

 

[AWD V8]

I have read a TSB on this problem.

Pull the wheel sensor out and clean it and the mounting surface.

Youtube link that shows how to test the sensor. https://www.youtube.com/watch?v=swM9sYptlks

 

[AWD V8]

Found it.
TECHNICAL
Bulletin No.: 03-05-25-007D
Date: May 01, 2009

Subject:
Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)

Models:
2002-2006 Cadillac Escalade, Escalade EXT
2003-2006 Cadillac Escalade ESV
1999-2006 Chevrolet Silverado
2001-2006 Chevrolet Suburban, Tahoe
2002-2006 Chevrolet Avalanche
2003-2006 Chevrolet Express
2007 Chevrolet Silverado Classic
1999-2006 GMC Sierra
2001-2006 GMC Yukon, Yukon Denali, Yukon XL, Yukon Denali XL
2003-2006 GMC Savana
2007 GMC Sierra Classic
2003-2006 HUMMER H2

Supercede:
This bulletin is being revised to add the 2007 Silverado/Sierra Classic models. Please discard Corporate Bulletin Number 03-05-25-007C (Section 05 - Brakes).

Condition:
Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.

Cause:
The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.

Correction:
Measure AC voltage and clean the wheel speed sensor mounting surfaces.

1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual.

2. Disconnect both the front wheel speed sensor connectors at the frame and harness.

3. Place a Digital Volt Meter (DVM) across the terminals of each wheel speed sensor connector.

4. Rotate the wheel clockwise approximately one revolution per second. The minimum reading should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual.

5. Plug the wheel speed sensor bore in order to prevent debris from falling into the hub during service.

6. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, scotch brite, or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion.

7. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor.

8. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (in Canada, P/N 89022218).

9. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (in Canada, P/N 993037).

10. Install either the original sensor or a new one in the hub. Ensure that the sensor is seated flush against the hub. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual.

11. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel. The voltage should now read at least 350 ACmV's.

 

[Mounce]

Just wanna point out that GMT360's are not included in that so the information is questionable if not inapplicable to the case at hand.

 

[AWD V8]

I know they are not on the list but the symptoms are the same. I don't remember what the sensor looks like but I'd be trying it if it fixes the others.

Just the thoughts of an S10 owner new to GMT.

 

[Mounce]

Understandable. Cleaning wheel speed sensors is a good first step though.

 

[MAY03LT]

Why can't autozone provide a tech II for cripes sakes.

I thought one of their loaner tools was an actron reader that could do abs codes.

 

[Mooseman]

To be able to read all codes, I use my Elm327 with Car Gauge Pro on my Android phone. Works like a charm and the $5 for the app is well worth it.

I agree on the sensors. Give them a cleaning and see what happens.

 

[Mark20]

Hasn't more than one person here solved the same problem by simply cleaning the sensors?

 

[AWD V8]

Dirty wheel speed sensors has long time been the bane of GM products. Cleaning has worked in many cases for the S10 crowd.

A wheel bearing that is going south can leave metallic debris on the sensor and cause problems.

 

[nagyiii]

Dirty or bad sensor. I had to replace one a few months after doing a wheel bearing.