Ok, I just replaced my master cylinder with a rebuilt one from autozone, and just replaced my lines with goodridge lines. So I go to bleed the system (I bench bled the MC first), and I can only bleed the right rear and the left front, and can’t bleed the left rear and right front. I double checked all the connections and they all seem solid and not leaking, but I’m guessing I have an air leak somewhere. What I’m not sure about is would the proportioning valve cause anything like this ever (since I think the two brakes I can’t bleed are from the same proportioning valve circuit)? Or could the MC be at fault? I think I bench bled it properly, it seemed to work. Basically, what’s happening is that if I pump the brakes a few times (6 or 7 usually), I can get a spurt of fluid to come out at the bleeder valve when I depress it and hold it again, but after that initial spurt, no more fluid comes out, just air. Anyone have any suggestions? I’m gonna sleep on it and recheck all the connections again in the morning. Should I put any sort of sealant on the threaded connections to the MC or anything? I didn’t and assumed I didn’t need to because of the design, but maybe I overlooked something when looking at the connections. Thanks in advance!
you do know that you have to close the bleeder screw before letting off the brake, right??
He he 
yep, definitely did thanx for the suggestion, I’ve been known to make stupid mistakes like that before
did you pump the brakes slowly?
also did you have a rubber tube right on the bleeder valve? so it makes a tight fit over the bleeder valve.
also isn’t the proportioning valve just control the brake pressure between front and rear?
Ya, I tried it all again yesterday, double checked all the connections again. This time I tried using my vacuum bleeder. All it would suck out was a combo of air and fluid, and it never got to pure fluid, or anywhere near pure fluid. I’m thinking I’ll disconnect all the lines today and maybe hook up a compressor to a few points and see if I can hear where the leak is. I’m gonna try reconnecting everything then too, and see if that helps. I may just take it to a shop and let them contend with it, but the earliest they could get to it is wed. of next week, so I’m gonna keep playing with it until then.
You may just have a problem with your bleeder screws. While you’re working on the brakes anyway, borrow a bleeder screw from a caliper you were successfully able to bleed and put it on one you can’t. Sometimes they clog.