Brake IDK

Brakes seem to lose compression when facing downhill, most notably at low speed. Brake fluid reservoir is full.
Ford f 250 xl 1993

 

Not sure what facing downhill means but if pedal is going to the floor it could be a bad master cylinder especially if no leaks are found!

 

Is this a fix-it problem or a replace-it problem?

 

If I remember correctly every master cylinder failure I've experienced had leaking around the master cylinder. They can be rebuilt but I've always just replaced them. Have you checked the condition of your shoes/pads?

 

Not sure what you mean by "facing downhill", but since you also mentioned "most notably at low speed", I'll assume that you mean when you are driving downhill. Driving downhill, particularly at low speed, the weight of the vehicle itself helping to propel it, would seemingly equate to lower engine speed. And if lower engine speed is indeed a factor, I think the first thing I would do is inspect the vacuum line for cracks, deterioration, etc., as well as the clamps being tight, and if that didn't pan out would check the engine vacuum. And of course this assumes that the brakes themselves, specifically rotors and pads, have been properly maintained.

 

The part of the Piston that connects to the brake booster was damaged/worn completely out so replacing the cylinder did the trick. I doubt that I did a professional job of bleeding but I am pleased with the result.