willsboattail

After a month of sitting in the garage, I took my 03 FX4 out to haul some leaves today and was shocked by a fading brake pedal at each stop.
The truck stops, but the pedal will continue to slip almost to the floor while sitting. Fluid level is fine and no leaks observed. Brakes were redone a couple years ago and truck has only 5,000 miles or so on it since then. 55,000 total miles on truck.
After a quick search of this forum, I have located 3 possible issues; a brake booster fail, an ABS Module fail, or a check value leak.
Am I on the right track here and what might repairs cost me????

serranot

https://www.f150forum.com/f6/brake-p...-150-a-157374/

Red-Ford

Sounds like you have air in the lines, pump the brakes a bit and see if it stiffens the pedal up. If not, you need to bleed your brakes.

willsboattail

UPDATE
Well, $278 later, after 2 brake master cylinders and full new brake fluid change/rebleeding, my mechanic threw up his hands.
Local Ford dealer gets their turn at it late next week
I did unplug the ABS Module just to see what happens.... Nothing different except ABS dash light came on. ABS Module may not be the problem either!!??!!??

serranot

Unplugging the ABS module will do *nothing* if it has an internal fluid leak. You have to test the HCU with a paper clip as diagrammed in the link I attached. It takes two people and about 30 seconds, so I highly recommend trying it. I'm virtually certain it is your problem.

willsboattail

Thanks, I was hoping that was now, NOT the problem.
NOW I,m depressed all over again.
Too cold here to spend the time outside testing.

UtahGuy

What a timely thread. Googling around for a fix to my sinking brake pedal was on tonight's to-do list., so thanks for the link @serranot. Are you still happy with your EBay unit?

serranot

Yup. Things work perfectly.

I actually had sticking calipers all the way around. Replaced the rear rotors, pads, and calipers with stock and replaced the front pads, calipers, brackets, and rotors from a 2002 Expedition. They are upsized a little bit but just bolt on.

willsboattail

Update
Truck is at the Ford Dealership and ABS module is finnished! about $1100 to replace it. Get truck back mid next week!
Wondering if my first Ford is my last!
OUCH

tonyroc14

It's an old truck. The newest version of these trucks is now 11 years old! What do you expect? Stuff is going to break. You want to save some money? Do this stuff yourself. What you had done is easy stuff. Master cylinders are easy to replace, the ABS module is a little more difficult, but IMO still pretty easy.