tommy99

Wow, so this brake job saga is finally over. I replaced the master cylinder, ABS unit, rotors, pads, calipers, drums, shoes, springs, and wheel cylinders. I would get a solid pedal when it was up on jacks but as soon as I started driving the pedal would drop down and start pulsating. I wasn't getting any check lights, and I bled the entire system and bench bled the master cylinder multiple times, but every time I would get on the road the pedal would pulsate up and down as soon as I pressed it. Well I finally figured out what was wrong after weeks of working on this thing. The dirty brake fluid didn't just destroy the rubber in the wheel cylinders, it also started eating up the rubber flex lines from the inside. They got so weak that as soon as I would apply the brake and build pressure in the lines they would start expanding and collapsing. The fluctuation of pressure in the lines would make the pedal pulsate up and down. After changing all of the flex lines I got a solid braking system.

I bleed my brakes every year, but this is a friend's truck, and it was heavily neglected. I doubt that fluid had ever been changed. I disassembled both wheel cylinders and they were pitted and scarred. To add to this topic.. The ABS system was also damaged. I'm guessing the damage was caused by the dirty brake fluid since it seemed to ruin everything else it came in contact with. The replacement ABS unit will be here in a couple of days. Once I get it swapped out, and everything is working, I will disassemble the old ABS valve body to see how bad it looks. I can post pics if anyone is interested.

It was two bad wheel cylinders. I was re-bleeding the brakes and one of them finally popped. Both wheel cylinders were slightly leaking but the dust boot was catching the brake fluid before it could pour out.

So I bench bled and swapped out the master cylinder. Vacuum bled all of the lines again with about 45 secs of vacuum on each line. I'm still getting the red check brake light and the pedal is soft and going to the floor. I'm not getting any leaks in the lines or bleeders. Has anyone had a similar experience? Is it possible there is some air trapped in the ABS? Would the yellow ABS light come on if there was air in it, because I'm not getting the ABS light. Any ideas?

I had the soft pedal problem before the bleed too. I don't think there is a lot of air in the system since I was pulling it through the lines using vaccum. I let each line bleed for about one minute and I sealed each bleeder screw while the machine was still pulling fluid through the line. I guess the master cylinder is the only thing left.

Yes, I adjusted them all the way up to where they had a decent amount of drag when I put the drums back on. They can't be adjusted from the back while the drum is on so I got them up as high as possible before I reinstalled the drums. I briefly get pressure in the pedal but then it drops and the check brake light comes on.

I have a 97 K1500 and the brake pedal would go to the floor when I pressed it. I did a full brake job on the front (calipers, pads, rotors). The rear shoes and drums were in good shape so I put them back on without changing. The brake fluid was black so I bled the reservoir and all four brake lines in correct sequence using a Mityvac 6835 brake bleeder. I bled all the lines two times just to make sure I got all the old black fluid out. Once I got it back together the pedal would only hold pressure briefly and then go to the floor again, and now the red check brake light will go on and off once the pedal drops. Any ideas? Thank you