I noticed a lot of posts on this issue and would like to add to it cause I'm pretty pissed right now. I just spent 2 weeks intermittently trying to get my car going. I did a K-H disc brake swap, new lines and a new combination valve. Front brakes were fine but rears wouldn't bleed. I did everything possible to get fluid to the rear but no luck using vacuum, buddy bleed, even a syringe to force fluid in from the rear bleeders. Nothing worked so I did the loosen a front brake bleeder trick to get the shuttle valve centered but nope nothing. Today I took the combo valve off for dissection, this is what I found. The lower part of the shuttle valve is jammed in the bore as if it was forced in, I could not even get it out using 150 pounds air pressure!!! The upper part of the shuttle is also a bit tight but it came out ok. The bottom plug leaked and the crush washer as well so as you can see I had to use hydraulic sealer or (goose poop) as some call it. $90.00 useless part I can't return so I'm screwed. Just want you all to be aware of these valves and if you purchase one take it apart to make sure everything is in order and not stuck.