Calipers or Accelerator Pedal Sensor, Cause overheating?

I have a 2004 Chevy Trailblazer. It recently started acting crazy. While driving
down the road, I suddenly noticed that the brakes became very hard and
while pressing the gas pedal there was no acceleration. I also noticed a
strange humming noise which I believe was coming from towards the engine.
Within several minutes it apparently began overheating (although the
instrument panel did not show that it was overheating) and the water boiled
over onto the ground. Someone in the parking lot walking by stopped and
told me that it was the calipers or line. After it cooled I cranked it and it drove
fine. I took it straight into a repair shop but they couldn’t figure out what the
problem was. They said that the only code it threw was for the “Accelerator
Pedal Sensor” and they reset it. It continued to drive ok for about 2 weeks,
then suddenly a repeat of the same issue.  Please can someone help me?
I’m desperate!!!