After applying brakes the front left brake doesn't want to let go and can't even spin the tire by hand when jacked up it's so tight. Vehicle obviously pulls hard to the left but strangely momentarily pulls to the right when braking hard and doesn't pull to the left until the brake peddle is released. Replaced the caliper and still does it (rotors and pads where replaced a year ago and are still like new as I don't drive it that much).

Is it the master cylinder going out? The unit where all the brake lines and reservoir connect is part number 1L3V-2C346-AA but I can't find it in any online ford parts catalog? I really want to get up and running for this holiday weekend so I can tow the boat. Vehicle is a 2004 Ford Lightning. Thanks.

 

if its just one side then its not the master cylinder. (if it were the MC then both front wheels would be locked up).

Some people claim the flex line could be "collapsed on the inside" and trapping pressure. I personally don't understand this and have never seen it. If that were the case - try loosening the flex line where it attaches to the caliper and see if brake fluid comes out under pressure. (WEAR SAFETY GLASSES!)
If it were the flex line, once you loosen the connection and release the pressure the caliper should release the rotor.

If that does not fix it, then I would guess its a seized caliper. Either the piston is bad or the sliders need to be cleaned and greased (although if its seized that tight you probably need to buy new sliders and maybe even a whole new caliper).

After you change it out, you will need to bleed the entire brake system.

If it were me... I would go ahead and replace the flex lines too while you are there... since you need to bleed the system anyway at that point...

 

Yea, I already put a new caliper on which came with new sliders. More than one person on another forum told me it's the lower flex line and that it's a "common problem". I bought both sides but I have to wait for the rain to stop to put them on and try them (no garage). Suppose to rain until Sunday here, but I'll come back and update the thread after I put the new lower flex lines on and test them...

 

It was the lower flex line. Real simple fix. Just wanted to update in case someone else runs into the same problem...