04 silverado brake problems

[roosterr58]

I have a 04 silverado Z71. I Changed power brake booster, master cylinder, front calipers and pad and new rotors. Bled brakes fine, but still will not hold pedal. |Originally when i drove it, it would act like the brakes would apply by them selves thats why i started changing stuff. |Any ideas ?

[maxwedge]

Welcome to AF. All the brakes dragged?, did you jack it up and check which or if all were dragging, what did you do to continue to drive, did they free up by themselves, any previous work done or an accident that could be related to the condition?

[roosterr58]

All of the brakes were locked. Let it set until it cooled down, and they released. I figured the master cylinder was not returning and changed it. |This truck had been in a flood, (I found out) ||The brake booster was full of water, so i replaced it and the calipers and rotors. |Bled the system, but still will not hold a pedal. |I dont know much about the abs or the other systems that control these brakes

[SLJ2137694]

Originally Posted by roosterr58

All of the brakes were locked. Let it set until it cooled down, and they released. I figured the master cylinder was not returning and changed it. |This truck had been in a flood, (I found out) ||The brake booster was full of water, so i replaced it and the calipers and rotors. |Bled the system, but still will not hold a pedal. |I dont know much about the abs or the other systems that control these brakes

If your brake light switch is a round cylinder (plunger) type of switch, check to be sure it isn't holding your brake pedal down a little. The usual way to adjust these switches is to pull back on the brake pedal. If you hear some clicks that may have been the problem. If you have a spongy pedal after all that brake work there may still be air in the ABS modulator. Try making some stops to activate the ABS and if there is air in the modulator this will help to move it out into the lines where you can effectively bleed the air out.

[roosterr58]

brake light switch not the problem, what is the correct way to bleed the abs module. Can i by pass this module? I am going to see if the new master cylinder is holding pressure and work my way down. VERY AGGRAVATING

[Sonny01]

I think the only way to properly bleed the ABS module is to take the truck to either a dealer or someplace that does brakes and has a scanner with ABS capabilities.

[SLJ2137694]

What exactly do you mean when you say it won't hold a brake pedal? Is the pedal sitting at normal height but spongey when you apply it? Is the pedal sitting lower than it should be? How did you confirm the brake light switch is adjusted properly? Are the brakes still trying to self apply and drag? Are you able to activate the ABS system when doing a hard stop, if so this can help move air out of the ABS module. GM dealers use a hand held diagnostic tool called a Tech 2. This tool is used to bleed the ABS module.

[Chevy-SS]

I remember test-driving one of these trucks (Z71) - brand new - at a dealer. The brakes were so horrible I was afraid of crashing. I mean, it was like the thing had grease on the rotors or something. The pedal was soft and the stopping power was negligible. I drove it right back to the lot and parked it, lol.

I have a 98 Sily and its taken me a lot of work to get a decent pedal. I think these Chevy trucks just have a crappy design, perhaps the components are too small. I installed new master cyl, new calipers and rotors, and rear brakes (drums) too. I bled the system 5 or 6 times over a year or so. The pedal was still soft, very annoying. The brake pedal got much firmer after I took it to dealer and had them bleed the ABS mechanism. However, I still drive cautiously, the brakes are not that great.................

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[j cAT]

Originally Posted by roosterr58

brake light switch not the problem, what is the correct way to bleed the abs module. Can i by pass this module? I am going to see if the new master cylinder is holding pressure and work my way down. VERY AGGRAVATING

if any moisture enters the brake fluid the calipers/abs will require replacement as well as cleaning of all brake lines.....use of a vacuum pump and nitrogen gas will purge lines of moisture..... small amounts of contamination will damage ABS......like if rust/sediments entered/created in the system.... brake fluid absorbs moisture and then rust is created inside the system............GOOD LUCK!!!!!

[roosterr58]

Hi,I have changed master cylinder, power brake booster,front rotors, pad and calipers. I bled the master cylinder before i put it on. I bled the front brakes 10 or 12 times but could never get any kind of pedal at all. We pumped the pedal 10 times, held it, bled front and rear brakes. Nothing but fluid came out.It took 10 or 12 times of pumping before any pressure would build up. Replaced the master cylinder again, same thing. No front brakes at all, rear brakes lock up, no pedal, have to pump and pump to get any thing. Not enough brakes to activate the abs. Why no front brake and all rear?

[Chevy-SS]

Originally Posted by roosterr58

Hi,I have changed master cylinder,..... No front brakes at all, rear brakes lock up, no pedal, have to pump and pump to get any thing. Not enough brakes to activate the abs. Why no front brake and all rear?

Have you had the ABS unit bled by a dealer? Also, did you properly bench-bleed the master cylinder prior to installation?

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[j cAT]

Originally Posted by roosterr58

Hi,I have changed master cylinder, power brake booster,front rotors, pad and calipers. I bled the master cylinder before i put it on. I bled the front brakes 10 or 12 times but could never get any kind of pedal at all. We pumped the pedal 10 times, held it, bled front and rear brakes. Nothing but fluid came out.It took 10 or 12 times of pumping before any pressure would build up. Replaced the master cylinder again, same thing. No front brakes at all, rear brakes lock up, no pedal, have to pump and pump to get any thing. Not enough brakes to activate the abs. Why no front brake and all rear?

ABS must be defective /or air. as stated small amounts of contaminates will damage ABS.....


how can you bleed front if no braking on front?
rears always braking? did you take it out of park?park brake off?
make sure the rear calipers are not binding

you will need a abs scanner tool to bleed ABS.....you cannot bleed ABS without activating ABS ...

[roosterr58]

Truck is heading for the shop Monday to bleed the abs system. THanks for the help.