That's interesting. I don't know if it would happen 27k miles after I bought the car though. How many miles did you have on your H3 before it happened?

 

7000 km.

 

Mike..It could be air, I'm not sure..but I don't think it is..Because, if it were air, it would be spongy on the first push everytime and then pump up if you continue to pump the pedel rapidly...A bad master cylinder seal will hold and then just let go, and it could happen a very critical moment..Then hold again until conditions are right for it to let go again..It happens toa lot to all cars and not uncommon...As far as the cap seal, you'd notice brake fluid on the reservoir and everywhere if that leaked...Even if it did leak, it would not affect the braking action becuase the cap is vented anyways...Have it checked out soon bud, no sense playing Russian Roulette.

 

My God Mike, I wouldn't pull a trailor if there may be a potentail brake problem. We don't want you to get hurt.

 

dont forget about the parking brake if it happens again
it will stop the truck since its on a cable system and not in the fluid system
you might already know this... just thought id say it incase someone didnt know

 

Or worse..wreck the HUMMER........Kidding bro..just kidding

 

If it were me, I wouldn't drive it until the dealer gets ahold of it, and if you must drive it there, expect there to be no brakes evrytime you use them. Down shift to every stop and to slow down, that way if they are gone you aren't traveling at a high rate of speed when they fail. The unfortuneate thing about the parking brake, according to my dealer, is that is is just for parking and won't apply enough force to be effective for stopping, especially from a high speed. This is another reason to downshift.

If you think it will be inconveniant to be truckless for the weekend, think of how inconveniant it will be if the truck is wrapped around a light pole, or another car because the brakes failed.

 

Yeah I thought about all this. I know about the parking brake. I actually checked everything out last night. I have no leaks in any of the brake lines, the master cylinder looks fine, I checked the fuses, the fluid is full and clean, and I have no brake or error codes on the OBDII detector. Maybe I did accidentally hit the clutch since I was half asleep.

I drove it to work today and it was perfectly fine. I kept a good distance though, but so far so good. I called all 3 dealer's in my area. All of their service departments said they have not had any master cylinder replacements come in. The main dealer I used to go to said they have had a few people come in for that problem, and found it was nothing but air stuck in the system just like KTM said. He said it probably won't happen again, but if I want to bring it in I can. They didn't see any need for me to though. They also said the other customers had the same situation, where it happened the first time they pressed the brake after they started the car cold. I guess maybe it's just one of those things that happens with an H3 like everything else. Still, I'm going to bring it in to be checked. I'm no fool (even though I may seem so at times)

 

did you try putting a magnet on your Master cylinder? works wonders

 

MURPHY'S LAW...