New caliper won't release
 

I just put two new front calipers/brake lines on. Bled with a power bleeder at 8 psi. Brake pedal is firm, but I think one of the calipers is stuck. Start the car and after braking a couple times, it feels like I'm fighting the brakes. What would cause this?

Rubber brake line from the fender to the caliper may be bad. They can swell and cause the caliper to stay applied after braking. Open the bleed screw and if the caliper releases then it is probably the hose.

Dave

the rubber hoses collapse internally, so while it may look OK from the outside, it will pass fluid to the caliper when you step on the brake pedal, but will not return to the m/c. This will also give you a hard brake pedal. Follow the advice above to diagnose bad hose.

You would not be the first to change a sticking or stuck caliper out before checking the flex hose for problems first. Always make a habit to just loosen the flex hose at the caliper before unbolting the caliper if it is suspect.
Applies to american cars as well.
Remember nothing is lost as you will have to remove the flex hose connection to change the caliper out anyways. On an old caliper it is just sometimes easier than fighting with a rusty bleeder if you have no heat. Plus you might loose the bleeder screw and still find you had a bad flex hose. You then might have created a double header for yourself. I did it once myself but never again.

perhaps your rears are now causing problems... did you bleed them too?

vstech,
I hadn't heard that air in the lines can cause a stuck caliper. I'll try bleeding them again tomorrow maybe.

And they sure should be able to take a whole lot more than 8 psi. I do mine at least at 20 psi. You get a lot more than that when you apply the brakes.

How were the calipers when you changed pads?? did the pistons retract easily and smoothly?? if it is a bad caliper, I would suspect that there were tell tale signs when you did the brakes.

did you remove the caliper, or just do pads, prying the cylinder back in??

Were the calipers new or were they overhauled? Did you replace the front brake lines and the brake hoses?

Even though you have just put new parts on test like you where just starting to check out a brake malfunction. If you can locate the side with the suspect caliper try pushing the pads back. If no go loosen the bleeder as its new and moves easy. See if it caliper will retract then. If it were both sides the master cylinder would be suspect. Only one side rules that out. Also be careful reaching a decision. As even a new hose for example could be faulty. Not likely but possible.

The sympton appears to be: the fluid is being trapped in the caliper. the caliper is not releasing. bleed it. try the brakes again. If you get the same hard pedal and the caliper won't release, change the hose. I'd suggest doing both sides. new calipers=new hoses!
No more problems up front. The master won't cause this kind of problem that I can remember.

seems the lines are new, everyone....

There are brake lines and there are brake hoses. It's not clear to me what is new and what isn't.

If your hoses are new, I'm going to suggest a tipped piston in your caliper. This will require removal of the pads and a visual inspection. Usually best to take caliper off rotor to view it.