Driver's Side Brake Caliper Keeps Locking Up

I have a 1999 Tacoma 4x4 Base Model with 4 cyl 2.7L engine. On sunday, I was driving on the highway and the gear selector gave me a chattering noise so I pulled over. I couldn't see anything wrong in the cab or under the truck, but I was still a bit unnerved, so I started again, but this time on the side road. As I drove, I felt like there may be a transmission issue, because it felt like it was having a hard time shifting. Eventually I realized this was because my driver's side front brake caliper was locking up.

I drove it further than I should have and burned up the piston seals so I went and picked up a new caliper and I installed it and some new pads, bled the brakes and topped off the resevoir with fresh fluid.

I drove it for 40 miles, then it locked up again yesterday morning. Fearing it was probably the rubber brake hose, I replaced that. It drove fine for another 10-15 miles before locking up again this morning.

Other pertinent information:

The brake fluid does look pretty dark to me, could it be as simple as a brake fluid flush?
It does seem to happen pretty soon after brake (seems like the fluid can get into the caliper, but can't get back out??)

Any thoughts on what could be causing this?

Thanks guys! Sorry if this has been addressed! I searched, but couldn't find this specific problem.

 

Might as well start cheap and easy: flush the brake fluid.

 

What about the rotors? you may have a step in the rotor that the pad is catching on, or something like that.

 

Frozen caliper I would bet. I would replace both if it were me. Check rotors and definitely bleed the brakes

 

Look at the steel lines coming into that Caliper .

Like you state OP fluid is getting in but not out .

Crushed or kinked line .

Then it is possible you got a poor quality rebuild lots of junk out there today .

 

If I were just to throw parts at it I might start with the rubber brake line, they can act like that because fluid in under pedal pressure but not so much pressure to return it though a inward swollen constricted rubber tube.