2000 GMC 3500 rear brake bleeding

[ken_man_1]

And here we go!

Sometime during the year, one of the guys I work with decided to put hydraulic fluid in the master cylinder reservoir. This just turned fun.

The gasket on the reservoir swelled up and fluid was leaking out of it. I didn't know until I pulled the cover. With that said....

I am proactively replacing the master and front calipers. What made me look into it was that one for the front calipers were freezing up, and I had just did the front brakes in the beginning of the year.

Now, with that said...I'm bleeding the lines before I reinstall the new calipers. I got all of the contamination from the front lines, and went through and bled out the front brakes. All is well in the front end.

However, the rear lines still need to be purged. So, I decided to crack the rear line at the T, just to flush out the contaminants, and I can't get anything out back there.

I bled the master as per instructions I found from a regular poster on another thread (Thanks 2000CAYukon!), and I get fluid from the master to the ABS unit on the fender. I'm not getting anything out of the ABS unit, tho.

Is there anything that can be done outside of getting a scanner that will run the ABS pump to get it to go? Do I need to replace the ABS unit due to the hydraulic fluid contamination?

Thanks for looking, I appreciate any contributions.

[gmtech1]

Ahhhh, brake fluid contamination. Gotta love it. As you know, anything rubber that was exposed to the contaminate needs to be replaced, that would also include the flex hoses. If the contaminate made it through the ABS module, which it did if it caused the caliper seals to swell, then it should be replaced also. The only way I am aware of doing a "automated bleed" of the ABS module is with a GM Tech 2 scanner.

[j cAT]

all the non metal parts must be replaced. the ABS valve body unit ,master,front rear calipers. then using alcohol I forget which type flush out all the metal lines then blow out. then start the reconstruction of all the calipers/hoses/abs/master.

good luck...

[ken_man_1]

That's kinda where I was. The ABS unit was the only thing I was unaware of.

Thanks for the heads up. Much appreciated!!

[DeltaP]

Any solvent alcohol will do for a flush as long as you blow it all out. Then blow out any condensation that forms during alcohol evaporation when blowing high pressure air through it. Sounds like $$. Esp for the ABS unit. Good luck.

[ken_man_1]

Well, since I've been on the defensive about the contamination, I went through and replaced EVERYTHING...hydroboost (because it was sweating fluid, so just precautionary) to the calipers and wheel cylinders. I had an ABS unit that was from a donor vehicle....known good.

Before the hydroboost replacement, the pedal would slowly sink to the floor. But, it would stop just before the floor. Brakes were bled many times. So at this point, I'm guessing the boost failure internally. Replaced the boost.

Same issue. I took it to a shop where they were able to bleed out the ABS unit and verify no issue of air whatsoever. They call me saying it's ready.

I go pick it up, and I might as well have fed the birds with the money they charged me to repair the issue. It does the exact same thing.


Has anyone else had this issue? Possible p/s pump? No issues with steerability, no noise.

[j cAT]

Originally Posted by ken_man_1

Well, since I've been on the defensive about the contamination, I went through and replaced EVERYTHING...hydroboost (because it was sweating fluid, so just precautionary) to the calipers and wheel cylinders. I had an ABS unit that was from a donor vehicle....known good.

Before the hydroboost replacement, the pedal would slowly sink to the floor. But, it would stop just before the floor. Brakes were bled many times. So at this point, I'm guessing the boost failure internally. Replaced the boost.

Same issue. I took it to a shop where they were able to bleed out the ABS unit and verify no issue of air whatsoever. They call me saying it's ready.I go pick it up, and I might as well have fed the birds with the money they charged me to repair the issue. It does the exact same thing.


Has anyone else had this issue? Possible p/s pump? No issues with steerability, no noise.

so the brake pedal slowly goes to the floor ?

master or a small leak .

hydo boost system no power brakes or steering.