I have a '99 F150 4.6l XLT
When applying the brakes everything is fine until I''ve nearly stopped, then suddenly I hear a grunting noise upfront and have no brakes. If I release the pedal and re-apply the brakes again more often than not the brakes will work. This problem has suddenly started occuring, last year I replaced the pads and rotors on all 4 wheels.
Anybody have any suggestions?

 

sounds like a bad master cylinder. does the petal go all the way to the floor? and I assume you have verified there are no leaks and there is brake fluid in the master cylinder. If this is the case the cups inside the master cylinder are allowing the brake fluid to bleed back through thto the master cylinder. The grunting noise is the brakes slowly loosening up.

Lance

 

You might want to bleed the brakes. Does the pedal feel soft? Like it has some give in it, kind of mooshy? If so, then there is air in the line, and they just need to be blead. Also, if you are loosing some fluid, one of the front caliper could have a small leak.

 

Thanks Guys,

There are no leaks and there is plenty of fluid, the pedal is a bit squishy. I'll bleed the brakes and see if thet helps