Brakes went out took to a mechanic replaced master cylinder. calipers rotors pads and 1 hub. picked up truck drove 30 miles front brake locked up and caught fire.

did this 3 times replacing the parts again not master cylinder. no fix I replaced parts and portion valve no fix brakes work. get soft.. then lock up.

any ideas.

 

Brake hoses?

What are you driving?

 

ABS buggered?

 

yes replaced both brake lines 1998 dodge durango

 

Most likely ABS module.
Pull the fuses out and see if it makes a difference. If it does, then you know for sure.

When you say brakes lock-up do you mean cruising when suddenly the wheels lock?
Or at some point you try to brake and the pedal becomes mush and brakes lock-up?

Because the second is a symptom of no brake fluid/broken master cyl. The brakes will work when empty but basically lock the wheels one you depress all the way.
I learnt that when the U-bend at the front wheels corroded and failed, emptied the fluid instantly, then locked-up.

 

It is literally impossible for the brakes to lock up when the fluid leaks out.

 

Try it, then let's talk about it.
Though I am pretty sure it pulls the ebrake cable for that, so that would make the rear wheels lock, not front.

 

Yes!!!
This is what happens:
brake hoses get clogged (pieces of rubber). When you push brake pedal, pressure opens the hoses and pump brake fluid in. They swell and keep pressurized fluid in, holding pads. Pads don't get released, because clogged hoses keep pressure in.