If I had to guess, it is one of two things, the lines are seeping around the fittings. the clamps have very little tension. they rely mostly on the tension of the hose over the barb. when they get old and brittle, they start seeping sometimes. Nice thing is, you need to remove the motor to change the lines. The other thing, if your lucky is that someone didn't tighten the bleed screw down when they last bled the pump. It is the philips/8mm on top. It has a slot cut in the side so when you bleed it a turn is all you need. good luck., see you next year