Originally Posted by
wheelzzs
The fluid is not returning to the m/c. (I assume its not returning through the ABS system)
I've seen this happen when the flexible brake hose needs to be replaced. What happens is a piece of the hose material breaks away from the wall inside the hose and flaps. This has the effect of being a one way valve. It lets the fluid go in one direction, but when the fluid tries to return, the pressure holds the flap tight and blocks off the hose.