I just replaced the master cylinder on Jim Sleeth's car, and it don't work. Jim bought a rebuilt master cylinder from NAPA. We bench bled it, connected the lines, bled the calipers in the proper order, etc. Everything looks normal, no fluid leaking anywhere. If we let the system sit for more than 15 seconds and then step on the pedal, it almost goes to the floor. With about 3 more pumps, it firms up properly and stays firm for as long as we continue to pump it. But if we let it sit for more than 15 seconds then the pedal goes soft again. Apparently we just got a bad cylinder from NAPA. The original cylinder was leaking, so that was the reason for getting into it. Can anyone say what could possibly be wrong in a master cylinder to cause this? Or could we be overlooking something else? I don't see how trapped air could cause this symptom. We bled the system by the good old-fashioned two person way. Jim pumped the pedal while I turned the bleed screws. We used up two pints of Castrol GTLMA dot 4 because we wanted to thoroughly flush out some Dot 3 he dumped in there to make the car temporarily drivable (after the reservoir went dry due to the old leaky master). The Dot 3 never touched the new master. If it caused a problem in the calipers, I suppose they would hang up or leak. But it isn't doing this. Walt _____ Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/DMCForum/ * To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx <mailto:DMCForum-unsubscribe@xxxxxxxxxxxxxxx?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .