Hey all!

Just asking for some tips, while I wait for a dry day to diagnose some kind of brake leak. (2005 Edge 3.0, rwd) The pedal sinks all the way to the floor. I topped up the reservoir with fluid, and bled some air out, which definitely helped - but over the following week, the pedal lost its stiffness and is now spongy and limp again. I'm not observing any leaks or puddles, and the fluid level has barely changed even as the pedal got categorically softer, so maybe it's the master cylinder; but once I get a free sunny day I'm going to examine the lines more thoroughly than I've been able to, and find out. I wanted to know, any suggestions for doing a good job of diagnosing? If it is a line, does anyone know what size brake line is necessary for replacing lines? I'm new to this.

Thanks for your suggestions!

 

Fluid level in Master WILL go down if you have a leak
So if it didn't go down then no leak

Hold out the Parking Brake release handle and then pump the parking brake pedal several times to see if it engages higher and higher up in pedal travel as you pump it, this adjusts the rear brake shoes, and no you can't over adjust it, so pump away
People often don't use the parking brake so rear brakes never get adjusted, this causes excessive pedal travel because rear slaves(wheel cylinders) need more fluid to expand enough to press shoes against the drums

And could just be time to do new rear brake shoes

But yes, failing master would be first guess if pedal is not holding pressure and fluid is not leaking

Ford used different size metal brakes lines over the years, even different sizes in the same year, lol
Fronts are usually 3/16" and the 1 line to the rear 1/4"

 

Thanks Ron! That's very helpful; I'll give the adjustment a shot, but living in a hilly area I use the parking brake every day. But I'll try it anyway!

Just to clarify, at the end of the summer (I was gone for a few months and had to leave the truck parked) the MC reservoir was mostly (not completely) empty, and it was after that, that I topped it up, bled the brakes, and topped it up again. Since then, it's barely lost any fluid, even while losing all the pressure it had after the bleed.

Thanks for the suggestions, I appreciate the help!