Sticking caliber. Flush the brake system and install fresh brake fluid, then bleed the brakes. If that does not help, replace both calibers and brake pads on the axle where the brakes are grabbing.
Check you brake fluid and lines. It may be as simple as bleeding your brakes.
Did you check the vacuum hose or did you refill the brake fluid?
One possible cause is a misadjusted brake pedal. If the push rod is pushed in slightly all the time, it will block the tiny fluid return port in the master cylinder bore, trapping fluid. As the fluid heats up and expands, it is blocked from returning to the reservoir, so it applies the brakes slightly. This heats the fluid, so it expands, applying the brakes more, which heats the fluid more, which applies the brakes more...
I have to believe that it would be a bad wheel cylinder that controls the back brakes.
Bad torque converter? Bad Power steering pump or low fluid?
you may be low on brake fluid
No it is a totally different fluid. It can sometimes be used as power steering fluid in a pinch. I would strongly advises you not to try it. The viscosity is different and it won't flow thru the lines properly. This will in turn cause your brakes to fail.
you have brake fluid leak in your brake system somewhere that need to be check.
it might not have enough brake fluid or your ABS is going bad. i would take it to a shop cause that can be serious.
most likely is air in the system so you need to bleed brakes , or you have a component leaking fluid. inspect all calipers and wheel cylinders for fluid leaks. it might be a master cylinder leak / malfunction also. but air is most likely.
I would say that it would cause your Anti-Lock Brake System (ABS) to fail i.e if you slam on your brakes really hard they will lock up and you will skidd to a stop and possibly off the road. It may also leak brake fluid so I would keep an eye on your brake fluid levels. If it gets low a light will come on in the dash. If your car runs OUT of brake fluid your brakes WILL NOT work. My suggestion if you have go to your mechanic and have the value fixed. Brakes are the most important thing in your car.
Check the brake fluid level in the reservoir there is a sensor there that will make the light come on if your level is low.