My Intro/2006 Yukon Brake Issue

[6977Gregyver]

I'm currently a small engine mechanic but I've been a automotive mechanic for a long time. I was also an electrician for about 15 years. I consider myself a Jack-Of-All-Trades master of one. Some people might think that driving a truck over the road is a piece of cake, and actually it is, but to be really good at it take experience and a certain feel for it. Driving is my preferred profession and I am the best driver I know. Enough about me.

I own a 2006 GMC Yukon that has been giving me a headache lately. On occasion while driving the brakes will start squeezing the calipers all by themselves and slow you down to the point where you have to pull over on the side of the road. Most times they will release themselves in about ten minutes and I can begin driving again.
The last time this happened I had to loosen the nuts on the master cylinder and pull it away from the firewall about a 1/4" before I could move the vehicle. I recently installed new rotors, new brakes - front and rear, new master cylinder, new line from the power steering to the master cylinder, new power steering pump - this Yukon has Hydro boost. I am at a loss to understand why the brakes keep applying themselves. Has anyone experienced or heard of this problem and a possible solution?

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally help you with your question; however, other members on this Forum that are much more knowledgeable than me will chime in.

 

[Miami-Dade]

Welcome from NYC!

 

[rockola1971]

Umm I dont think your brakes are "applying themselves". You have air trapped in your brake system and making it worse by cracking lines loose at the master cylinder which cause the brakes caliper pistons to not withdraw fully when brake pedal is released.

 

[S33k3r]

No trouble lights on the dash?

 

[6977Gregyver]

Umm I dont think your brakes are "applying themselves". You have air trapped in your brake system and making it worse by cracking lines loose at the master cylinder which cause the brakes caliper pistons to not withdraw fully when brake pedal is released.

The brakes are applying themselves. There is no air trapped in the system and I didn't crack the lines loose at the master cylinder. I backed off the nuts securing the master cylinder to the firewall about two turns. Someone recently told me that the engine needed to be running when the master cylinder and the lines were bled. This doesn't make sense to me. What will be accomplished by having the engine running when the system is bled versus what will be accomplished bleeding the system when the engine is not running? I know how to properly bleed a master cylinder and the wheel cylinders. Just for the hell of it and to prove myself right, I went ahead and bled the master again with the engine running. And I bled the wheel cylinders again also. All to no avail. My efforts were to no avail. Nothing has changed. I'm reaching a boiling point with this Yukon. For four years in a row I have had to replace all of my brakes and discs. Does anyone have any ideas as to what is causing this problem?

 

[Fless]

Likely the rubber brake lines are collapsing. Are they original?

 

[rockola1971]

The brakes are applying themselves. There is no air trapped in the system and I didn't crack the lines loose at the master cylinder. I backed off the nuts securing the master cylinder to the firewall about two turns. Someone recently told me that the engine needed to be running when the master cylinder and the lines were bled. This doesn't make sense to me. What will be accomplished by having the engine running when the system is bled versus what will be accomplished bleeding the system when the engine is not running? I know how to properly bleed a master cylinder and the wheel cylinders. Just for the hell of it and to prove myself right, I went ahead and bled the master again with the engine running. And I bled the wheel cylinders again also. All to no avail. My efforts were to no avail. Nothing has changed. I'm reaching a boiling point with this Yukon. For four years in a row I have had to replace all of my brakes and discs. Does anyone have any ideas as to what is causing this problem?

You bled the brakes old school style didnt you? You likely have air trapped before or after the ABS solenoids. I learned the hard way on one of my 2003 Tahoes. I couldnt get the thing to bleed for nothing. Nothing remotely close to a solid brake pedal. Even tried to gravity bleed. I locked the brakes up activating the ABS and that helped get some but not all the air out of it while bleeding again and again. I finally broke down and bought a Tech 2 clone and use the auto brake bleed function which uses the ABS pump to bleed and actuates the solenoids for each tire and bleeding was done in less than 20 mins. Brake pedal solid as it ever could be. I will never do it without my Tech 2 clone again!

 

[6977Gregyver]

I will take that into consideration. There are some things I wasn't aware of till just now. I can admit when I'm ignorant of the facts. And my apologies to anyone if I offended you with my decisive but errant statements in a previous post.

 

[6977Gregyver]

No trouble lights on the dash?

No trouble lights on the dash.

 

[6977Gregyver]

Likely the rubber brake lines are collapsing. Are they original?

Yes they are original. How would the lines collapsing cause the brakes to 'apply themselves' randomly while driving? Is the rod from the master cylinder that connects to the brake light switch and brake pedal adjustable?

 

[Fless]

I don't know about the MC rod. It may or may not be the case for yours, but the rubber brake lines have been known to get soft and collapse, not allowing the calipers to fully retract the pads after braking. Maybe heat causes an issue while you're driving, that's just a WAG to consider.

Air in the system is much more likely a problem.

 

[MassHoe04]

I have seen what @Fless has described with collapsed hoses. That happens fairly frequently on old rubber brake lines.

Are you sure the caliper pistons are moving freely?

My rear calipers were fine when I bought it. The brake pads were already worn down and really thin at the time, so it wasn't long before I did new rotors and pads.

It turned out that the brake pads had been on for so long and warn down to the metal backing, that over time corrosion build up behind the pistons. When it was running the worn pads and the pads wore down more and more, the piston was way out and only moved a small bit to apply the thin pads.

So when I put fat new pads on there, the pistons were now pushed back into the crusty part of the cylinder. First application of the brakes, the piston did push out to apply the pads to the rotor nice and hard. But... The cylinders would not move back to release at all! The rotors were smoking and glowing cherry red!!! It was new calipers for me... Luckily, there was no damage to the rotors or pads.