EDIT: PLEASE go to the last page and read my latest posts. I keep having different problems with the brake system and I need all the help I can get with it. THANK YOU.


Well, this was a first today. I had to call a flatbed for this truck. I was on the Garden State Parkway. I went to stop and the pedal went to the floor and the brake warning light blinked. It felt like I only had 25% brake force. I managed to cut across 2 lanes of traffic, take an exit and pull into the nearest parking lot. I checked the brake lines. No leaks. I checked the brake fluid. Overfilled to the top. I called for a tow. They took it to a repair shop. Now I got to wait for tomorrow for a verdict. Of all times for this to happen. I just hit 90k on Wednesday and I drove over 300 miles since then. Am I looking at a bad repair bill? What could it be? I just had the brake fluid flushed at 72000 last year and new pads and rotors done all around over the past year. Fronts in July 2009, rears in Dec 2009. I do admit, this was the first and scariest emergency I have ever had on the road. I just hope it is the last.

 

I'm not sure what would be causing the problem with all the things you named that were ok, well at least you didn't end up hurting yourself or the car.

 

Well with no leaks, overfilled fluid, pedal going down to the floor and the warning light, based on what I have seen on the forum, I was thinking of the master cylinder at the time. The brakes felt a bit soft a few miles before this, but since it was hot out (90F), I thought the brakes were hot. But when I got the sudden low pedal soon after that, low pressure and light, I knew it was a serious problem. Could it be an internal failure of the master cylinder? Could something inside it like a seal or gasket popped all of a sudden and caused this? Could this have been prevented? I had all new fluids put in last year as I said, including new brake fluid. When they flushed it last year, it was overfilled. Could this have caused it?

 

im thinking an internal leak in the master cylinder or abs block, but i would lean towards the master cylinder first.

 

Ok, the shop called Saturday morning. Master cylinder was leaking internaly. They replaced it and flushed the system. That fixed the problem- For 200 miles EXACTLY. I finally made it to southern NJ (my original destination, but 24 hours late), but on the way back home TODAY: ONLY 15 MILES AWAY FROM WHERE I BROKE DOWN ON FRIDAY, the brakes started getting softer and softer over a few miles until the pedal went to the floor and the warning light stayed lit. I had the same exact situation as the original breakdown on Friday except the warning light stayed lit and it happened faster! Unfortunately, I was far from an exit this time and I had no choice but to pull off to the side of the Garden State Parkway on the grass and call a tow truck AGAIN since I knew that driving without properly working brakes was asking for serious trouble. The tow truck driver tried the brakes and confirmed that the pedal was at the floor and the warning light was on. Then he winched it up onto the flatbed. I had it towed to the same place I was at on Friday. Once it got there, the tow truck driver tried the brakes as he was unloading it from the truck and said they felt almost normal. The mechanics at the shop test drove it and could FIND NOTHING WRONG WITH IT. They said it worked perfectly. They refused to do anything in terms of fixing it. After trying it again and noticing that it was somehow fixed, I decided to slowly drive it home (160 miles). I made it home without losing brakes again. Then I realized: What if they did replace the master cylinder correctly and they did bleed the brakes, but didn't do the bleed properly? What if there is an air bubble in the system that worked it's way into the master cylinder after 200 miles of driving and made my brakes almost completely fail and then after calling a flatbed again and taking it to the shop, it worked it's way out and they worked fine? Maybe in the ABS block? Isn't there a special bleeding procedure for ABS brakes? Could an air bubble explain today's failure? I wasn't getting an ABS light. Only the red BRAKE light when the pedal was able to go to the floor. I am going to have the entire system checked and bled again to make sure there are no bubbles because I REALLY don't want this to happen again. Especially on a mountain road. Good thing this was on a highway where I could easily pull off the road or just out of traffic. Good thing that I was also driving slow and I was able to get it off the road and stop it with the little pressure I had left.
The tow truck drivers and the Parkway employees who dispatch the trucks were great and very professional. My respect for them increased big time this weekend. They even were able to get me a flatbed when I asked for it. I didn't think the 4x4 trucks could handle a wheel lift truck without damage.

 

Ok, I took it to the dealership (for once) and they did a brake flush and a quick brake inspection. They were both shocked and baffled by this incident and how the brakes failed a 2nd time. Aside for their usual custom of finding something else "wrong" and a $900 estimate for rear pads, turn the rear rotors and new rear backing plates since the right rear one has a hole 1" wide in it (no thank you. I just had new rear pads and rotors done in December 09 and I had the brakes checked in January 2010 and again when the brakes failed on Friday.), they found no other problems. The 3 items I just mentioned obviously have nothing to do with the master cylinder failing (even the service consultant confirmed this). The pedal actually feels better and the car stops quick. I don't know how this is possible, but it actually seems fixed. The fluid is full and the brakes seem okay. If this fixes it permanently, then it explains that there was air in the system that only appeared after 200 miles of driving which then caused the 2nd brake failure and how it somehow fixed itself (or maybe the shop that replaced the master cylinder somehow realized they messed up and fixed whatever it was after it was towed there the 2nd time)?

 

After all that has been done to this truck over the past 4 days, should I be afraid that the next time I step on the brake the same thing will happen a 3rd time? The master cylinder was replaced and the fluid was flushed twice. The brakes failed and somehow fixed themselves 200 miles and 2 days after the master cylinder was replaced. What could have caused it? An air bubble? I managed to drive it the 160 miles home after that and another 20 to the GMC dealership for the flush. The brakes have been working fine (actually the pedal feels a little (like a hair) better), but is there a chance this can happen a 3rd time? I have to drive back upstate tomorrow (125 miles) and I REALLY don't want to have to call another tow truck because AAA didn't even cover the 2nd tow.

 

I would assume that there was some air in the lines and that is why it wasn't working right.

 

A little bit of air would make the brakes almost completely fail (brakes get softer and softer until the pedal to floor, warning light, very long stopping distance) 200 miles after a master cylinder replacement and flush and then they would mysteriously fix themselves after the truck was unloaded from the flatbed? Only air would make the same thing happen again? I just hope GMC knows their stuff and did the 2nd flush correctly because I don't want to have to go through that hell again! The manager at the shop in NJ said that if the master cylinder was defective it would not have fixed itself.

 

Well it is one thing after another with this truck. The GMC dealer wasn't kidding. My rear left pads are gone. I went to wash the truck tonight and afterwards when I was moving it, they were making alot of noise. The parking brakes were fully released. I pulled into the garage and pulled the wheels one at a time. The rear left had no braking material left and it was making noise as I rotated the wheel and it felt like it had alot of resistance. It is just so funny is that I had it checked multiple times over the past few months and noone noticed it. I didn't even know I had only 3 good brakes. The right rear still had plenty of material left. I already know I need new rear pads. I am going to get those done tomorrow, but what other damage could it have caused already? Am in for another large repair bill? This is totally insane. Up until Friday, the truck was perfect. I had just past 90k and then all these problems started. I just had new rear pads and rotors put in late 2009. I already know I am not going back upstate until this is fixed. Now I am afraid to drive my favorite vehicle because it seems to have a grudge against me for some reason even though there is no reason for it since I keep it very well maintained and I don't abuse it. I don't know how this grudge is possible, but it seems that it is the case. I have suspended all further trips with this truck until this is all sorted out. I really do hope this is just a case of cheap or a bad batch of brake pads and nothing else because I have never heard of pads wearing out this fast unless it was sabotage by another shop.