2000 Safari - Rear end trouble.

Been to three garages, two say nothing is wrong. Other says wheel bearings.


Problem:
Rear breaks make horrible grinding/scraping sounds and don't work when applied at very low speeds. Pedal becomes locked in place and in order to stop must be released and re-applied. This only happens at VERY low speeds (parking, stopping at red lights).

Garages seem to be baffled... I think its something that should be an easy fix for a mechanic? They have even taken it for test drives and put it on the analyzer... We need this fixed ASAP, stopping in parking lots and red lights is to the point we wont use the van! problem seems to have gone from happening once in a while to fairly often... We have an appointment with yet another garage Monday morning.

Is this the ABS engaging? I'm thinking wheel speed sensor?


Thanks

P.S: This problem started right around the same time as the other problem we have. I don't think they are related, but you never know... maybe a wide spread electrical issue? Other than that this van has been faithful and trouble free since we bought it, sad to see it so rough all of a sudden... other issue: http://www.automotiveforums.com/vbulletin/showthread.php?t=977333

ABS activation below 5 MPH is a common problem and usually caused by rust accumulating around a wheel speed sensor. Your 2000 has a sensor on each front wheel and one in the transmission tail shaft that monitors both rear wheels simultaneously. An ABS scan tool will reveal which sensor is causing the problem, (most likely a front sensor). Without the scan tool, you can try removing both front sensors and clean the mountings. This article tells how to diagnose and repair it. Let us know how it goes.

Brakes - Low Speed (Below 5 MPH) ABS Activation

Bulletin No.: 02-05-25-006B

Date: January 05, 2006

TECHNICAL
Subject:
Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface) Models:
1999-2000 Cadillac Escalade
1995-1999 Chevrolet Silverado (Old Style)
1995-2000 Chevrolet Suburban, Tahoe (Old Style)
1995-2003 Chevrolet Astro Van, Blazer, S10
1995-1999 GMC Sierra (Old Style)
1995-2000 GMC Yukon, Yukon XL (Old Style)
1995-2001 GMC Envoy, Jimmy
1995-2003 GMC Safari Van, Sonoma
1995-2001 Oldsmobile Bravada

Supercede:

This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (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 wheel speed sensor mounting surfaces.
1. Raise the vehicle on a hoist.
2. Disconnect both the front wheel speed sensor harness connectors.
3. Place a DVM across the terminals of each sensor connector.
4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's.
5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor.
6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service.
7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion.
8. 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.
9. 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 (Canadian P/N 89022218).
10. 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 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037).
11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub.
12. Install the rotor, the caliper and the wheel.
13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's.

Is this an AWD? The rear wheel speed sensor is on the transfer case along with sensors for the Xfer case system. Make sure you are checking the correct sensor.

Right again! Wheel speed sensors, problem resolved.

Thanks for posting back with the repair. Did you diagnose and repair it yourself?

Thanks for posting back with the repair. Did you diagnose and repair it yourself?

Diagnosed myself (with the help of the forums!), had professionally repaired, we no longer have a garage to work in. :shakehead Working out in the winter weather isn't worth it!

Thanks for the help.

Right again! Wheel speed sensors, problem resolved.

They don't call him the Old Master for nothing, you know.
















Wait for it....



















He really IS old.

Thanks guys.... :)

I have two favorite things that I say to my customers after a repair: "Well, I guessed another one right." Or, "I made an appointment to get my crystal ball fixed, I guess I can cancel the appointment."

Honestly, after a few years of listening to people describe the symptoms, ya kinda get the hang of it. The key word being "listen". Newfie452 nailed it in his first post.