Hey Dave;
The fire was at the right rear axle. When it caught fire the bearing had gone out and melted the seals.
Then the fluid caught fire and drained out passed the bad seals. Just how hot the brake fluid got is anyone's guess.
The axle got the steel rim hot enough the pop the tire and catch fire, then it warped the axle which had to be replaced.
I am not sure how hot the fluid got near the master cylinder though since it all drained out on the ground.
I have never used a brake pressure gage, how do you hook that up Dave???