Help needed: About 2 yrs ago the brake booster check valve failed requiring excessive pedal force followed by a brake master cylinder failure. I replaced the brake master cylinder and went to bleed the brakes but sheered off the L front bleed valve and subsequently replaced the caliper. I was never able to bleed the brakes and took it to a local Midas shop. They were also unable to bleed the brakes and concluded the new brake master was bad, replaced it and rebleed the brakes which worked well for about 5 months. I took it back to the Midas place the following Spring, they again were unable to bleed the brakes and again replaced the brake master and rebleed the brakes but the pedal was on the floor within a couple of days. No fluid has leaked out at any of the calipers or the lines as far as I can see. The reservoir is full and yet the pedal goes to the floor (but does return). Has anyone experienced this? Could this have something to do with the other hydrolic device below the brake master? Should I repeat bench bleeding of the brake master, and rebleed all four calipers again, perhaps with colored brake fluid? Would using a "speed bleeder" help? The weather is getting nice, any help or direction would be greatly appreciated.