1990 Ford F150 Brakes apply themselves?

1990 FORD F-150
57,000 MILES • V8 • 4WD • AUTOMATIC
Avatar
CRAVINBOB
  • MEMBER
  • 1 POST
My brakes seem to apply by themselves when I am driving in town 35mph and just coasting, like off and on pressure to the pedal. Almost feels like down shifting then up shifting quickly. Also makes a ticking sound that quits with slight pressure on brake pedal. Put the truck up on blocks, put it in drive while running and depressed brake pedal, master cylinder made a grinding or chattering sound when almost at the end of braking pressure then noise stopped at full brake pedal travel. I replaced pads shoes front calipers a while back and brakes work fine otherwise. Power boost unit shows that fluid at one time leaked a bit from master cylinder, paint crinkled, but no fresh fluid leak is visible now. Applying brakes causes idle to slow down some too.
Feb 2, 2008 at 5:40 AM
Advertisement
Avatar
MERLIN2021
  • CAR REPAIR CONTRIBUTOR
  • 17,250 POSTS
First thing to check is fluid contamination, draw some fluid out of the master put it in a cup of water and swirl...it should be a milky white and NO oil beads floating in it...Get back to us with the results...
Feb 2, 2008 at 7:17 AM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.