Vibration came and went

While travelling to our vacation destination in our 2001 GC, a vibration started. It felt like it was coming from the wheels but I couldn't pinpoint which one. Pulled over and checked all the lugs since I rotated tires 2 days prior but all were fine. Checked for the obvious and all seemed well. Started off again and it was worse. The further I drove, the worse it became. It forced me to pull over again. Except this time when I went to pull over, the brake pedal went to the floor. Pumped it a few times(quickly I might add)and got to a stop. Decided to limp along for a few more miles until I could get to an exit with some service stations/parts stores...just in case. But when I pulled out the 2nd time, there was no vibration whatsoever. And a few miles down the road when I started to stop(expecting to have to pump up the brakes again) all was fine. Never had a problem the rest of my vacation or on the trip home. The best I can dream up is a brake cylinder hung up. Maybe due to a stone getting behind a brake pad????? I don't know. Anyone have a clue as to what might have happened. One side note, when I did lose pedal the first time I checked the brake fluid, and it was higher in the master cylinder than it was before I left. After they started working fine the brake fluid was at the level it should be in the master cylinder.

I think you are correct about the brake. You probably had a brake caliper hang up and the brake slightly overheated and caused the vibration. I would check the front calipers, pads and rotors for any damage. If a stone caused the problem you may have a large gouge in the rotor. I would also be concerned about what caused the pedal to go all the way to the floor in the first place as it may happen at a very critical time.

I believe the pedal going to the floor was some result of the caliper hanging up? You seem to be very knowledgable about the mechanics of vehicles. Me, I'm more into troubleshooting electric(by no means an expert by any sense of the word). I respect your opinion and wonder if you could tie in the pedal going to the floor with a caliper hanging up under any circumstance. I'll be pulling the wheels within the week to check for any damages you mentioned may be possible as a result of the brakes heating up.

Anything is possible but I would be more worried about a problem in the master cylinder at this point. Usually when a caliper hangs up there is no relief of the pressure unless something breaks, like a hose or metal line. In some cases when the master cylinder starts to go bad there will be a noticable loss of pressure and then it will rebuild pressure for a period of time, sometimes for long periods and then the problem will reoccur. I would check all the brakes, both front and rear and all the brake lines for leaks. If you have drum brakes in the rear check the wheel cylinders for leaks as well. The fact that your pedal went to the floor has me concerned and you really need to try to find a cause. Once again it could have been the caliper but I really doubt it!!!

Thanks for the quick reply! I'll definately heed your advice and check everything out. I may go one step further and have a professional take a look at it. Since it's not a present problem, I feel the trained eye will probably have a better chance of spotting a potential problem. Thanks again! I'll let you know what they find.