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Need help on brakes.

GM GIMP

By GM GIMP
in Ask A GM Technician

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GM GIMP

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I just got through replacing the brakes on my '94 S10 blazer. It's a 2wd

4.3 W engine with 126,000 mi., front disc and rear drum. I replaced pads, rotors, bearings, calipers, shoes, drums, master cyl, all the rubber hoses, wheel cylinders, spring kit, and power booster.

 

After the installation I adjusted the rears up to snug and began to bleed the system. I used both a vacuum pump and the old fashioned two man pump the pedal and release fluid methods. I couldn't get the pedal to come up. I swapped the master cylinder again thinking maybe I got a bad one. I even tried

cycling the antilock by stopping on a rough road. All that did was lock the front wheels; I had to unplug the antilock unit from the 12 volt source to unlock the wheels. I tried it three times with the same result each time. So I bought a used antilock unit and installed it. The unit worked without locking the wheels but I still cannot get a good pedal. The antilock light still comes on and the brake light comes on when I press the pedal and it goes almost to the floor. Is there anything else I can do or does the dealer need to take over from here? I do feel that air is still in the system but I don't know how to get it out. I've used three quarts of fluid so far. PLEASE HELP!

 

Sorry for the long post.

  • 3 weeks later...
GM GIMP Enthusiast

GM GIMP

Posted
  • Author
Posted
I just got through replacing the brakes on my '94 S10 blazer. It's a 2wd

4.3 W engine with 126,000 mi., front disc and rear drum. I replaced pads, rotors, bearings, calipers, shoes, drums, master cyl, all the rubber hoses, wheel cylinders, spring kit, and power booster.

 

After the installation I adjusted the rears up to snug and began to bleed the system. I used both a vacuum pump and the old fashioned two man pump the pedal and release fluid methods. I couldn't get the pedal to come up. I swapped the master cylinder again thinking maybe I got a bad one. I even tried

cycling the antilock by stopping on a rough road. All that did was lock the front wheels; I had to unplug the antilock unit from the 12 volt source to unlock the wheels. I tried it three times with the same result each time. So I bought a used antilock unit and installed it. The unit worked without locking the wheels but I still cannot get a good pedal. The antilock light still comes on and the brake light comes on when I press the pedal and it goes almost to the floor. Is there anything else I can do or does the dealer need to take over from here? I do feel that air is still in the system but I don't know how to get it out. I've used three quarts of fluid so far. PLEASE HELP!

 

Sorry for the long post.

 

 

 

 

 

 

OK Then, Since nobody seems to know how about this: How does the dealership service Dept. bleed a Kelsey-Hays anti-lock unit? I see two bleeders on top of the unit but when I open them nothing happens. :thumbs:

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
OK Then, Since nobody seems to know how about this: How does the dealership service Dept. bleed a Kelsey-Hays anti-lock unit? I see two bleeders on top of the unit but when I open them nothing happens.

 

We've never bled the unit itself by those two bleeders on the anti-lock unit. I'm not really sure what they're for and I've never seen anything from GM about using those to do any sort of bleed procedure.

 

We have an automated bleed function built into our scanner that we use on these. Prior to having that function, we did just what you tried... taking the truck out and putting it into an anti-lock stop to activate it and try to get the air out of it. That didn't always work and I can remember fighting some of these for quite some time. The automated bleed works well to get the air of out the unit.

 

Other than that, most guys in the shop prefer the ol' two man method. One pumps the pedal a few times, holds it, and the other cracks the bleeders at the wheels. We also have a vacuum bleeder and a pressure bleeder, but the two man method is still the preferred method.

 

I will add that one of the tech's has a older Blazer that he did everything to get the pedal up after making a repair. He automated bled that thing 'til he was blue in the face, tried the vacuum bleeder and manually pumped probably two gallons of brake fluid through it. He recently left for greener pastures, but as far as I know, he never did a get a good pedal on it. I'm pretty sure he's going to have to replace the anti-lock unit on it but I don't know if he ever did.

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