So I had warped rotors on our 2013 f150 ecoboost. It was bought new, now has 65,000 miles on it. Had the rotors turned and put it all back together with new pads.... then I had a soft pedal that would slowly go down to the floor, huh? Dang it wasn't doing this before. Oh well I thought must have ruined the master cylinder so I bought a genuine Ford master cylinder and replaced it and the pedal still slowly goes to the floor...What the heck is going on???

Any help would be appreciated

 

You've got a leak somewhere.

Spray everything down with break cleaner and look for damp spots.

Did you disconnect the hoses when you did the pads? Those copper crush washers can be a bear to get sealed back up sometimes.

Go back through everything you touched, step by step. The only way for the pedal to sink is for fluid to leak somewhere, either internally or externally.

 

You didn't mention if you did the brake job yourself, or if a shop did the work. But it sounds like a brake line was opened, and that you may have air in the brake system now.
Unk Bob

 

Brake job was done at my place by an off duty mechanic. The system was opened only when master cylinder was replaced.

Thanks y'all for the suggestions

 

Any chance the booster recall is the culprit? Normally a bad booster show up as a hard pedal. At least for the stuff I've worked on years ago.

 

Cleaned everything and no signs of fluid leaking, gonna try and rebleed the system

 

is it possible that you have a weak or damaged brake hose?

if the hose is bulging when you press the pedal it could present as a sinking pedal.

seems unlikely, though.

did you make sure to get the inner and outer pads correct? I ask because they look similar and many have made that mistake. I'm doubtful that this could cause your symptom, but if the caliper or pins are bent, or are bending under pressure I could see how it might cause a sinking pedal.

again, doesn't seem very likely.

I'm about out of ideas ... this is an odd one.

hard for it to act like a leak without it being a leak. I understand why you replaced the master, but I've bled the holy heck out of brakes before and never ruined a master - just seems unlikely that you ruined one and then replaced it with a faulty one, though this is how you describe the problem .... I'm about as confused as you.

 

sounds like there might be air in the system somewhere. Ive seen similar issues before where the brake fluid compresses air pockets in the system allowing the pedal to slowly sink to the floor.

 

My 2013 XLT 4x4 has the 'sinking brake pedal' too. It started when I two-footed the pedal un a steep grade. Replaced master cyl with a Raybestos. No help. Replaced with a NAPA rebuilt. No better. Paid the $ and got a genuine Ford. No better. Read about the ABS fix and replaced the ABS with a junkyard piece. Took it in to my trusted independent garage, where he did a quick hot-box evaluation and said he would need to do an in-depth. He replaced a switch in the ABS module, yet continues to get a bad signal from the Body Control Module, as well as dashboard faults. Ford is well aware that this is a chronic problem, they don't have a fix and they are stonewalling owners.

The dealer service depts will replace EVERYTHING (m/c, booster, complete ABS, BCM and reprogram) and end-up in the neighborhood of $4,800.00. And still no recall, no service bulletin, no customer concern. Yes, I'm disgusted.

 

OK, finally had time to figure it out....really warped rotors? I had em turned at oreillys and he must have chucked em wrong. Bought 2 new ones from ford and it's fixed. Go figure ??
thanks for all the help!

 

UPDATE I did a mix/match on my ABS module. The scrapyard unit had bad electronics, but serviceable valving. ( not perfect, but close) After installing, I did several bleed rounds, then my independent garage used his reader to cycle the ABS to bleed the air. The pedal is hard at first, and stops the truck easily, but if I'm stopped on a steep hill, it will fade somewhat.

 

As I was reading along I was wondering if there is a way to do this. I work on a lot of bikes with ABS and cycling the system via a test port is always required to relieve rear brake pedal fade. In fact, it's such a common problem that many folks install a small toggle switch permanently to do it. Stomping the pedal on a 2-wheeler may result in a slightly different scenario than doing so in a truck!