My brother in law is having some issues with his rear brakes. We did a complete bleed, changing the brake fluid. There is no air in the lines but when we try to use the brake pedal it goes all the way down. You can pump the brake a few times and the pedal functions better. However, after a few seconds it doesn't work right anymore. He has 37,000 miles on his 1800 retro and the brake pads are new. It was acting up before he put the new pads on and has never been right since. It starting acting the way at about 20,000 miles. Any input is appreciated.