3

Apologies for the long post- I hope I've provided all pertinent information.

I have an '02 Trailblazer with 173000 miles and recently installed all new FRONT suspension components, including upper and lower control arms, coil-over shock, sway bar links, upper and lower ball joints, CV drive shafts, wheel hub/bearing assemblies, rotors, pads, and calipers. The calipers are remanufactured parts.

After installation the front brakes were bled satisfactorily and a firm pedal was achieved. A test drive of about 2 miles was made, and it was determined that the driver-side caliper wasn't releasing as it should, and the rotor (which was also new) on that side overheated to the point of changing colors from silver to gold with blue streaks. Meanwhile the passenger side caliper worked fine. No discoloration of rotor.

It was quite difficult to remove the driver-side caliper to take back to auto parts store, but I was eventually able to pry it off the brake bracket.

Of course, brake fluid was leaking from front brake hose after it was disconnected. I put the end of the brake line into a container of clean brake fluid, but of course that didn't stop fluid from being pulled through the brake line by gravity. By the time I returned with another caliper and rotor, the brake fluid reservoir was empty. At no time was the engine started, nor was the brake pedal depressed.

I installed the new rotor and caliper and filled the reservoir. I cracked open the bleeder on the caliper and waited until the caliper filled with fluid, and then bled the system, being sure to keep the brake fluid topped off (I used a bottle made for this purpose that I got from HF.

I'm not having any luck. Bleeding the front brakes is not solving this issue. The brake pedal continues to go to the floor (it was fine before all this), and I notice that the ABS idiot light is now on. I've double-checked the wheel sensor connectors, since I also replaced the front wheel hub/bearing assembly on each side. I don't recall seeing the ABS light during the first test drive.

Any suggestions as to how to recover from this will be appreciated.

EDIT

I have some new information. When I first posted this question, the vehicle was still on jack stands. I decided to see what the brakes were like with the car on the ground.

What I found was that once the pedal got all the way to the floor, I could stop it, but it felt like there wasn't much contribution from the front brakes. I took it on about a 2 mile test ride over city streets keeping the speed to 30 mph or less. Though there was no noticeable change in the braking, the ABS light on the dashboard did go out and it stayed out.

3

It sounds to me that either one of two, or possibly a combination of two things have happened.

If the fluid level in your ABS pump has dropped to allow air into the pump or the fluid level in your master cylinder has dropped to allow air into the system here you could potentially have the scenario you describe.

I'm afraid I can't comment on brake bleeding procedure for your vehicle but on Volkswagen cars, there is a specific ABS bleed procedure which can be initiated with the car plugged into a diagnostic machine. This cycles fluid through the pump which purges trapped air.

  • 2
    It's called an automated bleed on GMs. it commands/pulses the bypass modulator valve. Normally this is done with a pressure bleeder. Fairly common when the master goes dry. OP should also bleed the rear brakes. – Ben Aug 10 '17 at 13:12
  • I will check into this process with a GM dealer. – STLDev Aug 10 '17 at 17:22
  • Thank you for the suggestion @Ben. I'll look into the procedure you mention. Agree that rears need to be bled too. – STLDev Aug 10 '17 at 17:23
2

As you didn't mention the vehicle pulling when the brakes were applied I assume both front brakes are effected to some degree. The first thing I would do is try to bleed the master cylinder. If the master cylinder went dry it could potentially have air trapped in it. After attempting that rebleed the calipers. As @Steve Matthews has stated the ABS module may also need to be bled. Some Chevy forums suggest that driving on a loose or slippery surface (wet grass,gravel,mud,etc) then rapidly apply (panic stop) the brakes so as to activate the ABS module. This may take several attempts. It may also require rebleeding the calipers yet again.

  • Thanks for you suggestion. The vehicle is not pulling to either side. Activating the ABS is an interesting idea I had not considered. – STLDev Aug 10 '17 at 17:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.