Passenger front brake locks up.

[JBostick85]

I have a 2005 Pontiac Vibe. I bought it August of 2013 and it was a great car. In December of 2013 I started to experience an issue with the brakes. The front passenger side brake was seizing up and not releasing unless I let the car sit for about 30-45 minutes. My first thought was a bad brake hose. I replaced both front rotors, calipers, pads, and brake hoses. The issue went away for about a month then it came back.

I have replaced a grand total of, (1) set of rotors, (1) set of calipers, (1) set of pads, both front brake hoses, (2) master cylinders, and (2) proportioning valves. This car does not have ABS. For a while when I was having this issue, I would free the line from the master cylinder to the proportioning valve and this would free the wheel. Lately, I have had to free the line from the proportioning valve to the front passenger wheel to release the pressure.

I have not replaced the actual metal brake line yet because I am constantly being told that this is not the issue. Can anyone give me any suggestions as to what may be causing this or if I am missing anything? I've been dealing with this for almost 10 months now and I'm tired of it.

I have recently been told that I should do a complete brake fluid flush of the system in case there are any air bubbles in the line but I'm not sure if this will fix it. I have bleed the brakes every time a part has been changed and I figured if there were air bubbles present, wouldn't it effect other wheels as well? I'm no mechanic so any advice would be awesome.

[Derf]

That is a tough one. Caliper, hoses, master cylinder and divider replaced should have fixed the issue. Not sure what caliper kit you got, did the new calipers come as a complete kit or did you have to reuse parts from the previous caliper? Their have been several reports of "sticking" caliper slide pins but nothing as severe as you are indicating. The metal brake line could be an issue if it was kinked or flattened. Brake pressure is somewhere around 1000-1400 psi, a flattened line would slow the low psi fluid return. But when you bleed off the line it releases the brake near instantly, which goes against the flat line theory. I am not sure how the proportioning valve is setup in the Vibe, but the problem may be in another line? I know some vehicles are setup that during a failure of one line they are designed to hold pressure. Replacing two proportioning valves, and seeing fluid come back from the affected brake line suggests the issue is elsewhere.

[JBostick85]

Inspection of all of the lines seems to be clear. No kinks or leaks of any kind. I am going to try a complete brake fluid flush tomorrow. As far as the caliper issue goes, all new hardware came with the caliper replacement. The one thing that I'm thinking is maybe the original issue may have been the proportioning valve but over the 8 months of diagnosing this, the caliper could have gone bad from the constant locking and not releasing. If the issue persist after the fluid flush, the next replacements will be caliper, rotors, and pads again.

[JBostick85]

Almost a year later and I'm still having this issue. I just noticed that I have some kind of a "union" with my brake lines directly after the master cylinder but before the proportioning valve. I can't figure out what this thing is called. Line comes from the M.C in to this "union". One line goes from the "union" to my driver front wheel and the other to the proportioning valve. Does anyone know what this thing is called?

[lannvouivre]

What hoses did you get? Maybe you need to do a system flush and get better quality hoses as well?