Ok, this might get long winded, but please read...

I have half a pedal. The truck WILL NOT lock up the rear wheels, at all!!! The first thing that I did, when I noticed the problem was put SSBC pads and slotted rotors on. Half because I thought it would fix the problem, half because I wanted to. You guessed it, that didn't fix it.

Next, I bled the brakes, in the correct order, (RR-LR-RF-LF), to the point that I cycled the fluid. And again, that didn't fix it.

I was reading a post the other day, but only half understood it. Something about having to have the brakes bled while electronically controlling the ABS??? Also, there was something about a wheel speed sensor corrosion problem/recall?

Some of the things that I feel in the pedal...
When I have to hit the brakes semi-hard, I feel the abs kick in, but it seems too early, like I should be able to get more solid braking before the ABS starts in.

Any help on this would be AWESOME, this is dangerous!!! And I am stumped.

 

Here is the service info on the possible ABS problem.

Document ID# 1548756
2002 Chevrolet Chevy K Silverado - 4WD


--------------------------------------------------------------------------------

Antilock Brake (ABS) Activation at Low Speeds (Clean Wheel Speed Sensor Mounting Surface) #03-05-25-007A - (Sep 3, 2004)
Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)
2002-2004 Cadillac Escalade, Escalade EXT

2003-2004 Cadillac Escalade ESV

1999-2004 Chevrolet Silverado

2001-2004 Chevrolet Suburban, Tahoe

2002-2004 Chevrolet Avalanche

2003-2004 Chevrolet Express

1999-2004 GMC Sierra

2001-2004 GMC Yukon, Yukon XL

2003-2004 GMC Savana

2003-2004 HUMMER H2

This bulletin is being revised to update the correction information. Please discard Corporate Bulletin Number 03-05-25-007 (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.

Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in the General Information sub-section of the Service Manual (SI Document ID #899664).
Disconnect both the front wheel speed sensor connectors at the frame and harness.
Place a Digital Volt Meter (DVM) across the terminals of each wheel speed sensor connector.
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.
Plug the wheel speed sensor bore in order to prevent debris from falling into the hub during service.
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.
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.
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 (Canadian P/N 993037).
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.
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.
Parts Information
Part Number
Description

01051344

 

The activation of the ABS is way above 5 mph...
but I will take care of that tomorrow. A few questions...

1. What, if any, are the visual indications of sensor head problems?
2. Is this intended to fix the half pedal that I am dealing with?
3. Assume that it doesn't fix the problem, what next?

Thanks in advance.

 

It will not help the pedal problem at all. I will look into that further. When you say half pedal I am assuming you mean you have no braking until pedal is depressed half way. Also I am guessing you have no warning lights or dtc's since you didn't mention any.

For the pedal I would suspect there is air in the system somewhere. I had the pedal problem with mine after I added the SS brake lines because I was unable to properly bleed the LR caliper cause the bleeder screw was stuck. I drove it like that for a couple days until the new caliper came in and it sucked, but as soon as I put on the new caliper and got the air out it was fixed.

I would check closely for any possible leaks and bleed out the master cylinder if you haven't done that already. Your master cylinder may be leaking or have air in it if you got everything else bleed well with no line leaks.

 

Here is another bulletin that may be of interest to you.

Message On (Tighten Rear Brake Caliper Banjo Bolts, replace Gaskets and Install Shields) #04-05-23-001 - (Jan 21, 2004)
Low Brake Pedal, Red Brake Light On, Brake System Warning Message On (Tighten Rear Brake Caliper Banjo Bolts, Replace Gaskets and Install Shields)
2000-2004 Chevrolet Silverado 2500 Series

2001-2003 Chevrolet Silverado HD 1500 Series

2001-2004 Chevrolet Suburban 2500 Series

2002-2004 Chevrolet Avalanche 2500 Series

2000-2004 GMC Sierra 2500 Series

2001-2003 GMC Sierra HD 1500 Series

2001-2004 GMC Yukon XL 2500 Series

Condition
Some customers may comment on a low brake pedal, red brake light on or the brake system warning message is on.

Cause
Under some extreme off-road conditions, debris may loosen the rear brake caliper banjo bolts causing a brake fluid leak.

Correction
Follow the service procedure below to inspect the rear brake caliper banjo bolts and gaskets and to install new slide bolts and rear caliper shield.

Verify the customer's concern.
Open the hood and install fender covers.
Clean off the brake master cylinder reservoir with brake clean, P/N 12378392, or equivalent.
Visually inspect the brake fluid level through the brake master cylinder reservoir.
If the brake warning light is on and the fluid level is low, continue with the next step.
If the brake warning light is on and the fluid level is NOT low, continue with Brake Warning Indicator Always On diagnostic (SI Document ID #699182).
Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information (SI Document ID #737224).
Remove the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels (SI Document ID #800427).
Inspect the rear brake calipers for signs of fluid leaks around the banjo bolt area on both rear calipers.
Clean off the banjo bolt area with brake clean, P/N 12378392, or equivalent.

Important
The banjo bolts copper gasket should not be reused. The banjo bolts may be reused if not damaged.


Remove the banjo bolt and discard the copper gaskets.
Assemble the two new copper brake hose gaskets and the brake hose to caliper bolt to the brake hose.

Important
Inspect both rear caliper banjo bolt torques even if only one side is leaking.


Tighten
Tighten the bolt to 40 N·m (30 lb ft).


Notice
When adding fluid to the brake master cylinder reservoir, use only Delco Supreme 11®, P/N 12377967 (Canadian P/N 992667), or equivalent DOT-3 brake fluid from a clean, sealed brake fluid container. The use of any type of fluid other than the recommended type of brake fluid may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.


Bleed the hydraulic brake system. Refer to Hydraulic Brake System Bleeding in Hydraulic Brakes.
Hydraulic Brake System Bleeding Manual (SI Document ID #745273)
Hydraulic Brake System Bleeding Pressure (SI Document ID #745275)
Remove the caliper bracket bolts.
Reposition the caliper and bracket on top of the rear leaf spring.



Remove the caliper guide pin bolts.
Install the two new brake caliper guide pin bolts from the Shield Kit, P/N 15188166. Tighten
Tighten the caliper guide pin bolts to 108 N·m (80 lb ft).





Install one shield and two nuts from the shield kit. Tighten
Tighten the shield retaining nuts to 45 N·m (33 lb ft).

Install the caliper and bracket onto the rotor.
Install the caliper bracket bolts. Tighten
For RPO JH5, tighten the caliper bracket bolts to 200 N·m (148 lb ft).
For RPO JH6/JH7, tighten the caliper bracket bolts to 299 N·m (221 lb ft).
Repeat this procedure on the opposite side of the vehicle.
Install the tire and wheel assembly. Refer to Tire and Wheel Removal and Installation in Tires and Wheels (SI Document ID #800427).
Lower the vehicle.
Top off the brake fluid reservoir.
Remove the fender covers and close the hood.
Road test the vehicle.

 

You are correct, there are no codes, and I only have actual brakes after the pedal is half way down. There are no leaks, anywhere. At least none that fluid is coming out of. Maybe a pinhole that air is seaping in through? ANd I will check on the banjos at the calipers tomorrow, as well.

You know, my father had mentioned something about bleeding the master, but he said that there would be a bleeder on it somewhere. I looked, and can't find a bleeder on the master anywhere.

short answer, no, I have not bled the master.

Is there a trick to bleeding the master that I haven't figured out?

I really appreciate all this.

 

There is not a bleeder on the master you just have to loosen the lines that come out of it one at a time. Same procedure as when bleeding the rest of the system instead you loosen and retighten the lines instead of a bleeder. You may have to re-bleed the rest of the system after bleeding the master.

If that doesn't help I would move on to checking out the master cylinder. You can unbolt it and check for internal leaks and if there are no signs of leaks behind the bolts there is a possibility the you may need to bench bleed the master. You shouldn't need to do a bench bleed unless the reservoir was run dry, but its not that hard to do if you can't figure anything else out. You just have to mount the master cylinder in a vise and get some nipples to be able to run some short plastic lines from the out master back into the reservoir and use a screwdriver or dowel to fully press the actuator for the master in a few times to cycle the fluid and bleed out any air.

If all that fails,um, could be a bad master cylinder? But I would get a second opinion before spending money replacing parts.

 

As mentioned above, check for air in the system, leaks, master cylinder, etc. If all of that is good, another problem may be a frozen slide pin or a siezed caliper. Either of those will give poor braking performance and a spongy pedal feel. Usually there will be a brake pull associated with those since it mostly happens on one side or the other, but not always...sometimes you just get the spongy pedal.

 

Thanks for all the ideas. I'll check tomorrow, throughout the day for any more, and post up with what I found tomorrow night.

 

I must be the publishers ***** fu**n clearing house winning truck. I have the truck that CAN NOT BE DIAGNOSED!!!

Looked at the wheel speed sensors, for the ABS system today, just got finished, and they look brand friggin new.

I guess thats a good thing. Today I bought a vaccuum bleeder, so tomorrow, I am going to re-bleed the brakes, in hopes that I get some air.

ps, this may be my last post, cause after this, the truck is getting the Malatov treatment.

PPS, any ideas, before I set the bitch on fire?