Brake mystery

Alright, heres what has been happening with my 2001 volkswagen passat. The brakes just started locking up on me. So i brought it to the volkswagen dealer and they said there might be contaminants in the brake fluid and since the brakes got so hot they said the calipers, pads, and rotors were all fried. So they replaced a bunch of shit and it cost me almost 3000 dollars. I go and pick up the car and about five days later the brakes lock up again. So back i go to the dealership. After leaving the car there for about 3 weeks they tell me that they have no idea what is wrong but say it could be the auxillary brake booster and want to replace that for another 500 with no garuntee that it will fix the propblem. So i grabbed my car and got the hell out of there (before leaving i asked them to just unplug the auxillary brake booster, since it is electrical to see if that will fix the problem before they replace it). Anyways, i take the car and before i get to my house the brakes lock up again. After waiting about 20 minutes (usually 20 minutes or so and the brakes will unlock and allow me to drive a bit more) i was able to get the car home. Since then i have been trying several things, like unplugging the abs, and the electrical connector that goes to the brake booster. I have also unplugged the vacuum line that goes to the brake booster and drove it around the block with no booster. Unfortunately the brakes still locked up. So what could be the problem. Bad calipers? But they replaced all of them. All i know is that i have disabled almost the entire brakes system leaving only the your brake pedal and the brake fluid in the lines. But the brakes still lock up. No booster, no abs, no auxillary booster, nothing.
What the hell could be the problem?

It's not locking up randomly, right? Just when you hit the pedal I assume. All wheels, or just one or more in particular? Did they check (or is there a) brake balance controller? Did they check the master cylinder?

The vehicle has disc brakes on all 4 wheels.* What i mean by locking up is brakes drag very badly.* Infact when i feel them dragging I pulled the car to the side and jacked up each wheel to see if all or just one of the wheels were binding up.* It appears that all four wheels are indeed binding. The brake pressure releases after waiting for a while (20 minutes or so) and the pedal frees up. I unplugged all the electrical parts of the brake system just to eliminate them from being a possible cause. *The dealer told me that the brake fluid might have been contaminated when the did all that work to the car but if that was the case then dont you think that the rubber brake hoses as well as the master cylinder might be damages to due contamination.* I think my next move should be to replace all four rubber hoses and maybe the master cylinder.* What do you guys think?*

I also hope they cleaned the system properly because I was told that if there is a petroleum substance in the brake lines that a simple flush does not do the job.* You have to actually blow the lines out and use some type of brake cleaner.* So if this was not done then i am also wondering if maybe my new calipers are shot as well.

Also is there some sort of check i can perform on the masters cylinder to see if it is binding up and not letting the brake fluid come back into the resevoir?

Check out #21 here: http://expert.fleetowner.com/brakes/2005/03/ It's about a truck, but I'm sure the procedure would be similar. Not sure about the cost of the gauges mentioned...

If yours is all four corners, it would have to be something farther up the line than the pistons at each wheel.

Did anyone ever get to the bottom of this problem. I have exactly the same symptoms on my 2001 TDi130 Sport Tip (UK). I am dreading booking it into the dealer for the reasons outlined in the thread. Any advice/knowledge I can acquire would be useful.

since its a 01 I would say its teh abs control module thats faulty.