Recently put new pads/rotors on a 2008 GMC 1500. Everything went as usual with the install. I usually crack the bleeder when pushing caliper pistons back in and then do a bleed when finished to get some new fluid in the system. Did the exact same process on this vehicle a few years ago and no problems. This time I am getting no pedal at all, it just goes to the floor. Even if you pump it it will not builld pressure. I initially got fluid and air and at times will get clean fluid then suddently a bunch of air, but all with no firm pedal. Thoughts?
Trouble bleeding brakes
- Thread starter mbaker
- Start date
master cylinder failure?
Sounds like air in the master. Any chance it ran dry during your work? Maybe the reservoir got low?
I had this happen with my 2010. I ended up bleeding each line from the bleed screw and topping up the master cylinder. I bet you will have to do this. Ive also had a master cylinder fail on the truck too years ago.
Never ran dry, never got below the min mark on the reservoir. Thats what is confusing, I've never had this be an issue before.
Last attempt, I tried gravity bleeding and I get some fluid flow then it just stops. Both front sides act the same.
Last attempt, I tried gravity bleeding and I get some fluid flow then it just stops. Both front sides act the same.
I've heard of the full use of the master cylinder stroke may cause problems if it has never gone there before.
I like to have the engine running especially for the rears to get the use of the power assist. Open the bleeder, hook up a hose and pump a few strokes not worrying about closing the bleeder between pumps. I've had to do this to my Accent one time to get the line fully open and flowing on one side.
I like to have the engine running especially for the rears to get the use of the power assist. Open the bleeder, hook up a hose and pump a few strokes not worrying about closing the bleeder between pumps. I've had to do this to my Accent one time to get the line fully open and flowing on one side.
Maybe try using a brake bleeder instead of a helper pressing the brake pedal.
Might need a scan tool to run the GM automated bleed procedure.
I like pressure bleeders on low psi, like 10-15 max.
Yes bleeding and using the full stroke of the pedal can peel the master cylinder seals on debris in the master cylinder bore. The bi-directional OBDII tool maybe all you need though.
Did one of the bleeders not seat fully, even though it seems closed? If it won't build pressure there's a leak somewhere.
In my experience, GM trucks require a pressure bleeder. I have the Motive products unit.
Update…. Success. I had all but given up when I thought I’d try again today after letting it sit overnight. Noticed pedal was firmer and pumped up hard within 2 or 3 strokes. Had my son help me this time and we bled the fronts out and got better, drove a little and bled again. Feel like it’s back to where it was, maybe could still be pressure bled at some point. I guess maybe sitting let some of the frothy air settle out and let it be bled out today. Either way I am relieved. Also adjusted rear drums as they were way loose which may be why the fronts wore so fast if they were doing all the work.