Your point is good to remember. An internal leak past the master cylinder piston plunger can cause the situation being discussed. And, a rebuilt master cylinder may also be faulty in the same way, since the leak only has to be small, such as caused by a slightly out-of-bore or pitted piston cylinder. (Remember, all those rebuilt units came off of cars having braking problems! I have had several instances of going through one or two rebuilt units to finally get one that worked. Buying new avoids this risk, but boy are they expensive.

And, if the new master cylinder is not "bench bled" at installation, you can have trapped air in the unit that is almost impossible to bleed out.

 

1999 f-250 super duty 2 WD RW ABS Replaced Right rear brake caliper and hose. Replaced front L & R brake hoses. I have bled the brakes for two days with out sucess. I aso vacuume bled the system, and bled the Master cylinder and both sides of the ABS. HELP ME!!!!!!!!!

 

The bleeders are on the top side of the caliper, right?

 

The caliper I just replaced has the bleeder on the bottom

 

Thank you Andym. Went back to the parts store and got the correct caliper. Bled system and brakes work great