Ok i am having problems with my brakes......when off it will build up a little preasure with a couple pumps and then i take my foot off the pedal and let it sit for a couple seconds and then push on the pedal and it goes to the floor?When running it is spongey and no preasure. when i rev it the pedal will go to the floor very easily..i have replaced the master cylinder,rear lines and bleed the brakes like 20 times. I am stumped.....any help?

 

Did you bleed the LPSV?

Are your rear brakes adjusted right? If your parking brake doesn't work there's a good chance they aren't... My truck was doing the exact same thing after I replaced my rear shoes until I got them adjusted nice and tight.

Did you bleed the master cylinder?