Volkswagen Repair: 1973 super beetle brakes, rear brakes, wheel cylinders

Question
When I push on the brakes they go right to the floor I replaced the front brake hose right side, both front wheel cylinders and the master cylinder. the rear brakes looks good. When I try to bleed the brakes they will pump up but after 5 minutes there is no pressure. when I bleed the the brakes I hooked a hose to the bleed screw and put the other end in a container with fresh fluid in the bottom then I had my son pump up the brakes I then broke lose the bleed screw       I did this until no air came out of the bleed screw and I did it from the farthest away from the master cylinder to the left front. This didn't do any good so I tried another way that I found on the Internet and i was done by placing the hose that was attached to the bleed screw in a bottle of brake fluid and brake lose the bleed screw and pump the brakes until no air was seen in the clear tubing. This worked better but I still have the same problem after a while I lose the pressure. what could be causing this?

Answer
Hello Chuck;
It almost sounds like there is a loose fitting, or union.  I'm sure you made them as tight as you could, but look them all over one last time.  The other possibility is there may be a "cross-threaded" union.  It's funny that you don't seem to say anything about a puddle of brake fluid from a leak.  If there is air getting into a closed system, it must be displacing fluid.  There should be a puddle someplace.

Look for that first.  I hope this helps.  Good luck!