Brake troubles 2003 2500HD with Hydroboost

[izzy_Britton]

Bought a 2003 GMC Sierra 2500 HD, that i am calling a complete and total basket case.

The previous owner had some brake issues over the coarse of ownership and rather than fix the problems he just eliminated the problem. by eliminate, i mean he removed calipers, brake lines, rotors, shoes, blah blah blah.

As a result of the PO's shenanigans, I have replaced the following parts with all NEW parts:

4 rotors
4 calipers
2 front flexible brake lines
1 rear flexible brake line
all brake pads
rear park brake shoes
master cylinder
hydrobooster
power steering pump

There seems to be little to no pedal. The pedal doesnt build pressure while pumping the pedal. With the engine off, if i remember correctly, if you depress the pedal a few time the pedal will get rock hard. This truck doesnt do that, not even a little bit.

I took the truck for a short 5 mile drive last night and there seems to be a drag on one of the rear brakes, ever so slightly, I can hear the drag with the windows rolled down but i cannot feel a drag.

Any ideas why the brakes will not build pressure?

the ONLY other part that i have not replaced is the ABS unit. I have a used one of these but i dread putting it on.

-Izzy

[izzy_Britton]

Bought a 2003 GMC Sierra 2500 HD, that i am calling a complete and total basket case.

The previous owner had some brake issues over the coarse of ownership and rather than fix the problems he just eliminated the problem. by eliminate, i mean he removed calipers, brake lines, rotors, shoes, blah blah blah.

As a result of the PO's shenanigans, I have replaced the following parts with all NEW parts:

4 rotors
4 calipers
2 front flexible brake lines
1 rear flexible brake line
all brake pads
rear park brake shoes
master cylinder
hydrobooster
power steering pump

There seems to be little to no pedal. The pedal doesnt build pressure while pumping the pedal. With the engine off, if i remember correctly, if you depress the pedal a few time the pedal will get rock hard. This truck doesnt do that, not even a little bit.

I took the truck for a short 5 mile drive last night and there seems to be a drag on one of the rear brakes, ever so slightly, I can hear the drag with the windows rolled down but i cannot feel a drag.

Any ideas why the brakes will not build pressure?

the ONLY other part that i have not replaced is the ABS unit. I have a used one of these but i dread putting it on.

-Izzy

[storm9c1]

If the pedal isn't building pressure, it sounds like you still have air in the lines or in the calipers. How did you bleed them after all of that work? Did you make sure the calipers were installed with the bleeders at the top? I've seen wrong parts have bleeders at the bottom and that won't get the air out.

[Captainfab]

I assume you have properly bled the entire brake system? With all that you have replaced, are you sure the valve in the proportioning valve is still centered? The lines to the hydroboost are connected correctly and there is not air in the system? If the steering is operating correctly, the hydroboost should be good.

[izzy_Britton]

Originally Posted by storm9c1

If the pedal isn't building pressure, it sounds like you still have air in the lines or in the calipers. How did you bleed them after all of that work? Did you make sure the calipers were installed with the bleeders at the top? I've seen wrong parts have bleeders at the bottom and that won't get the air out.

I would normally agree that there MIGHT still be air in the lines. I bled more than a gallon of fluid out yesterday with my wife pressing the pedal (good communication this time), I started at the right rear, left rear, right front and ended at the left front, just like i was taught forever ago. after all was done and the pedal did have slight pressure, but now anything near what i would expect or any where near normal, i RE-Bled the master cylinder, while it was on the truck and again my wife pressing pedal. after re-bleeding the master cylinder, I again re-bled the brakes again. the pedal never not any better than slight, and i mean minimum, hardly noticeable pedal pressure.

Originally Posted by Captainfab

I assume you have properly bled the entire brake system? With all that you have replaced, are you sure the valve in the proportioning valve is still centered? The lines to the hydroboost are connected correctly and there is not air in the system? If the steering is operating correctly, the hydroboost should be good.

with the above being said, Capt'n, please help me out here. Proportioning valve is centered? how would i check this? does this ABS equipped truck even have a proportioning valve? I am used to what the old proportioning valves look like on the 73-87 chevy trucks, but i havent seen one on this truck. the lines from the master cylinder go directly to the ABS unit under the cab and then the lines (at least the rear LINE) goes directly to the caliper(s).

yes the steering works correctly, and as mentioned before i am 98% certain i was able to get all the air out of the lines. I really wish i had a power bleeder just to make 100% certain, but doing it the old fashioned way there was no more air coming out of each bleeder when i stopped and moved to the next.

and yes the calipers are installed correctly and the bleeders are UP.

i am not a complete and total idiot, but i have never had anything newer than 91 chevy, and never anything with ABS on it so i have to admit that i am grasping at straws here and I am ignorant to these new systems.

Thanks for help, I am losing hair at an astonishing rate over this. the truck is a complete POS but i am beyond the point of no return and really need to make it road worthy before the nastiest of the nasty weather sets in, REAL SOON. my daily 68 c20 has no heater, defroster, or cab seals, its drafty to say the least and driving it for the winter is not a comforting thought in the slightest.

[truckdude239]

Frist thing is iyou have a scanner that will go into the abs system you need to recenter or rehome the abs pump you'll never get all the air out unless you do this

[truckdude239]

XIV. Multiple Posting - It is simply not acceptable to post your question more than once, or to post it in more than one forum. Choose the forum that your question or post best fits in, and place it there and only there. If, after posting, you feel it should be in another forum, private message the forum Moderator and ask if they would move it for you.

YOUR THREADS HAVE BEEN MERGED

[cableguy0]

Originally Posted by truckdude239

Frist thing is iyou have a scanner that will go into the abs system you need to recenter or rehome the abs pump you'll never get all the air out unless you do this

Absolutely. You cannot simply bleed the brakes on these trucks most of the time. You NEED a good scanner to run the abs pump bleed procedure. You will never get the air out and you will never get a good brake pedal if you don't.

[izzy_Britton]

I have a friend with a Solus scanner coming over after work. I hope good scanner is new/nice enough to be able to access the abs system. Will update once we try.

Thanks for the info.

[cableguy0]

Originally Posted by izzy_Britton

I have a friend with a Solus scanner coming over after work. I hope good scanner is new/nice enough to be able to access the abs system. Will update once we try.

Thanks for the info.

Yes the Solus can do it. It is in either troubleshooter or functional tests section. He should know exactly if he uses the scanner regularly. Its a quick procedure just follow the directions on the screen.

[kwmech]

If I'm not mistaken there are bleeders on a module that is on the frame rail under the drivers seat also. There is also a ground wire on that module that GM had trouble with years back.

[izzy_Britton]

Sorry for this stupid question, I just don't know and I am away croon home driving so I can't really Google it...

Is this a procedure that requires anything to be done at the caliper whilst performing the reset bcentering?

I ask simply to be prepared when he gets to my shop, I don't want to consume to much of his time late in the evening with surprises.

Thanks again everyone for the words of wisdom.

-Izzy

[truckdude239]

Yes the solus will re set it it what i use at work one you reset or recenter the abs just bled like normal

[izzy_Britton]

My buddy forgot his scan tool at work last night, hopefully we can get this done tonight. Then I can get it out of the shop and get busy on my wife's truck build.

I will update when I have something to update.

Thanks guys.

[izzy_Britton]

My buddy made it to my shop Wednesday evening, 15 minutes later the ABS bleed was done and the truck now has a much better pedal feel. I am still trying to get the brakes bleed after the ABS bleed cycle did it's thing, but I am fairly confident that it will be better. I should be able to finish bleeding the brakes tonight or tomorrow morning and I will take it for a spin to see if it will stop.

Updates tomorrow.

Thanks everyone for all the help. I never heard of such a thing. Lol. But heck, this is my first computer equipped, and ABS equipped vehicle.

[pound41]

Years ago the brake lines on my Mom's 2000 silverado rotted out. I had to replace all the lines. A GM Tech told me. You can also put it in reverse slam on the brakes a few times and then bleed the brakes. That will cause the abs module to push out the air. I did it then and it worked. Last month by daughters master cylinder went out. She ran it dry. Replaced the Master Bleed the brakes they wouldn't build up. Remember what I had been told. Went out slammed the brakes a few times in reverse. Bleed then again. Like new