1991 Ford Ranger 4WD with 4.0 engine and manual transmission.

Today I was up at 10,000 feet in Colorado with my truck to go hiking.
I live at 5000 feet and it was very steep highway roads coming home.
I have lived in the mountains many years and do not ride the brake instead
I downshift to slow down. The brakes worked fine all the way down the one hour
ride down to town. Once in town the truck had a very slight pull to one side
when I braked which it did not have before. I stopped for 10 minutes to do an errand.
When I got back it the truck and took off the brake pedal went all the way to the floor and I had no brakes…stopped with the emergency brake.

I checked the reservoir and it was full and no brake fluid leaking at the wheels or lines. Triple A took two hours to come and after an hour I tried the brakes again and now I had a pedal. It was not the normal pedal but it was able to stop the truck. I waited and got towed to my house.
I jacked up the truck and pulled all the wheels off and by now it was dark. I did not pull the rear drums but inspected the front brakes and Calipers and pads. On the left front the
Outer rim of the rotor and the inner circle, where the pads don’t have contact, are a pinkish red. The same color on the outside of the pads. Almost like dust. The outside of the pads also have white crustation. Please see pictures. The rubber dust cover on the piston of the caliper was brittle on the end closest to the pad. The other side has no discoloring. When I turned the rotor by hand it was harder to turn then the right side. I am guessing that it overheated but why? Is it hard to turn because of the overheating or did it overheat because it was hard to turn and the pads were rubbing. Why would I loose the brake pedal completely.
Has anyone heard of this happening?? I didn’t think it was possible to loose all brakes from overheating a rotor.
It is a dual circuit master cylinder so wouldn’t the rear brakes still work….and why would the pedal come back an hour later. I am wondering if I need to change the master cylinder besides the rotor and caliper and pads…and should I change the caliper on the other side. I just want to make sure this does not happen again. I am so anxious about what happened today because if the brakes failed 20 minutes earlier I would have went off the mountain. Any help is appreciated.

 

If a caliper sticks(fails to retract) then rotor and caliper will get very hot and brake fluid can boil, form air bubbles.

That could have been what happened coming down that long grade.
The pull was the good caliper working and the other one not working.

The loss of all brakes would be odd, I can see both front brakes not working because the air that was now in the system was absorbing all the pedal pressure so no pressure was getting to the good caliper.

The back brakes should have worked though, unless they were marginal already, you wouldn't notice that, since front brakes are used more when stopping.

 

That is definitely signs of over heating. I think Ron assessment is spot on. One thing you should not overlook is the flexible brake line. I had an old one swell up on the inside and restrict brake fluid flow. It would cause a strange momentary pull in one direction and then would work fine. It also caused the caliper to hang up. This was not on a Ford product but I think it could happen on any brand.

 

Update on Brakes and need help.
The left front caliper overheated so much the boot around the piston was burnt. The right rear wheel cylinder, when the rubber boot was pulled back, had large amount of fluid start coming out. Rear shoes were good and front pads still had pad.
I replaced master cylinder, front calipers, front brake hoses, front pads, Left wheel bearings, left rotor, right rotor machined, repacked wheel bearings both sides.
Front brake lines where they screwed to new hoses had rusted nuts on the end of brake lines. I used a dremmel and cut off the double flare and put new nuts on and double flared the ends with a flare tool.
Replaced rear wheel cylinders and brake shoes and machined left drum and new drum on right. Did not replace the air booster.

When I test drive the truck about 1/4 mile constantly slamming on the brakes to see if all is working properly, the front rotors get very hot. I can smell them. If I spray water on the rotors from a spray bottle you can hear the sizzle. The left rotor which was the side that overheated originally and which was replaced seemed hotter and stayed sizzling to water spray longer. Also the brake pedal seems like it is not how it should at 30mph slamming on the brakes...seems like there is a slight delay...and not a screeching stop that would leave rubber...is this normal?? There is rear abs so does this have anything to do with this. With my van, which does not have abs, I slam on the brakes and get instant braking response at the wheels and it will leave rubber.
Any thoughts are appreciated.