2001 Toyota Tacoma Brakes

Hi. I have a 2001 toyota tacoma 4x4 V6. Recently I replaced the left side brake caliper and the brake pads. I did bleed the brakes and made sure the reservoir was fullid to the line. The only thing that we did that was not standard, was use powersteering fluid instead of brake fluid because that is all we had available at the time. I figured that it shouldnt make a difference. Hovwever for a couple of days the brake pedal caught really late and seemed pretty soft, then it became really sensative and would practicaly through you through the windshield as soon as you touched it. Sometimes the brakes would even stick on. I then changed the right caliper a couple days ago, and bled most of that other fluid out and replaced it with dot 3 brake fluid. It seemed to work fine until last night it started catching right away again. And this morning the brakes stuck again. Im starting to think it could be the master cylinder. Im not sure though.