'04 Tahoe brake problem

Prior to today everything fine. Took off this am and after about 2-3 miles started to slow down. Thought engine was losing power but when I pulled over it stopped quickly on it's own. All 4 brakes were locking up and I could smell and feel the heat from the brakes. Pedal hard in the UP position. Sat for about an hour and the brakes freed-up. Normal pedal feel. Got back home and same as noted above - locking-up. Checked PS as well as master cylinder fluids - OK and not high or low. The PS fluid has a little color but is not burned and looks clean. PS belt OK. Steering not affected. No ABS warning lights. No brake work done recently. As before, after about an hour the brakes freed-up. One site said to look for fluid movement in the master cylinder reservoir. If no movement when pedal depressed = hydroboost problem. The '04 Tahoe has the plastic reservoir with only a small fluid fill - no big cover to remove. Couldn't see clearly but didn't appear to be any fluid movement. Hydroboost? or ??? I'm now down to "0" cars - any help would be appreciated.

It sounds like a problem with the master cylinder. I've heard of this happening before but not 100% sure in what the actual cause or fix was. Basically the master is holding pressure on the system. This is why the rotors are hot and the pedal is hard.

May not be your case, but I've seen this happen when clear p/s fluid was mistakenly added to the M/C, this caused the seals to swell in the master and the brakes locked. Or a bad hydro boost.