2006 GMC Yukon Power brake booster


New Member
Three years ago I bought a 2006 GMC Yukon. One of the first things I did was replace the rotors and pads. Within a year the new pads were worn down to the metal. I thought it odd that they would wear down so quickly. Not knowing the history of the vehicle I assumed that maybe the previous owner had run into a curb or something and that maybe there was some slightly bent calipers that caused the premature wear. I disassembled the brakes and inspected everything, looking for anything that might be the cause of the worn out pads and rotors. Not finding anything wrong I again replaced the rotors and pads and hardware and installed new calipers as well. These pads and rotors lasted 6 months. I finally realized that the brake pads were in constant contact with the rotors but they weren't creating any noticeable drag or slowing the vehicle down. This time I could only conclude that the master cylinder must have a lot of corrosion in it and dirty contaminated fluid. I replaced the master cylinder, installed new rotors and pads again, bled the system completely until there was clean clear fluid coming out of the bleeders. The brake shift interlock wasn't working correctly either so I replaced it and installed a new transmission shift cable as well. This seemed to have solved the brake issue and there was no more excessive wear . Unfortunately I didn't route the shift cable correctly and the output shaft of the transfer case rubbed a hole in the casing on the shift cable. I replaced the shift cable again and routed it correctly. When I was done with that, my wife took the vehicle for a ride and about a mile from the house the brakes locked up hard and would not release. This time I replaced the hydraulic brake booster, replaced the fluid in the power steering and bled the steering. Again, my wife took the vehicle for a ride and within a mile the brakes locked up again. I loosened the bolts on the MC and pulled it away from the Brake booster, then re-tightened the bolts and the brakes let loose. I followed my wife home and before we could get there the brakes locked up again. I've gone through the whole system again and I cannot find what is causing the brakes to lock up. Is it possible that the MC has gone bad? I don't know where else to look and I am getting a little frustrated and tired of spending so much money on this vehicle. I'm pretty sure that the problem is an easy fix but I cant see it. Any ideas on what could be wrong?


Gold Supporter
Brake hose expansion would be my thought. If a brake hose fails internally, it can let fluid thru, but not back to the brake booster. But usually that is on a single wheel, not all 4. Its fairly odd.


New Member
I appreciate your thoughts on this issue. I have to get ready for work so any additional thoughts will have to wait until I get to work. Thank you. I had never thought of hose expansion as a possible cause. Again, thank you


You say you unbolted the master cylinder and the brakes released. Is it possible that the brake pedal or linkage is not retracting completely? When you bolt the MC back on, does it feel like the stud in the booster is pushing on the piston in the MC?

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