chevy p-30 brakes

I've been wrenching for 45 years. Guess I didn't make it clear in my first post, I just replaced the front pads, rotors, master cylinder and bled all calipers. I've done hundreds of brake jobs. Brake pedal level started dropping on my way to Waldport oregon going up the grades, yes, up the grades! Had to go through several passes. But on the return trip I had to go over a 6k pass in Nevada. The brakes were not used going up the hill. The pedal went to the floor at the top of the grade, I had to pull over to let the brake lines and master cylinder cool off from the heat from the exhaust manifold. The master cylinder was Hot when I touched it. The steel brake lines that are 1 7/8 of an inch away from the manifold were to hot to touch. I don't think I can explain this any more clearly. The brake fluid was boiling in the master cylinder and brake lines. DOT 5.1 has the higher boiling point, but the exhaust manifolds can reach 1200 degrees. I bought the unit brand new in 98, no one else but myself has ever worked on this unit. The brake lines are in the original position, they were installed incorrectly or they forgot to install a heat shield.

No long runs up serious grades yet. I checked the flex lines, because boiling brake fluid can cause then them to delaminate internally, all flows are ok. Doesn't seem to be any damage to the abs unit. Remember the lines from the master cylinder lead directly to the abs unit. I may have gotten lucky in that I've caught it before any long term damage has been done.