Brake pedal going to floor

Tiny
RODGERH1
  • MEMBER
  • 1999 FORD F-150
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
Brake light came on. Needed brake fluid. Filled brake reservoir. Light went out. Everything okay. Two days later brake pedal felt mushy. Pedal eventually going to the floor. Replaced master cylinder. Pedal still going to floor. Found driver side rear wheel cylinder leaking. (Ah ha. That is what the problem has been all the time.) Replaced wheel cylinder and put new brake pads on both back wheels. Bled air out of both back wheels. Pedal still goes to floor! Okay, bad brand new master cylinder? Got another new master cylinder. Brake pedal still goes to the floor! Two bad master cylinders?
Help. Mechanic with thirty years experience has no idea. He is our fleet mechanic keeping thirty vehicles going. From pickup trucks all the way through farm tractors, bulldozers, to over the road semi's.
Thursday, November 9th, 2017 AT 11:51 AM

1 Reply

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
May still have air in system, did you bleed the master on the bench first? Also, try and isolate problem by using brake hose clamps and lock off all brake hoses. The pedal should be hard and firm, release clamps one at a time and see if pedal sinks all the way. I would also be re checking rear shoes and adjustments as well, just to be sure. Start here.
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Thursday, November 9th, 2017 AT 3:42 PM

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