Hello!  My 2006 Ford E350 Super Duty van w/6.8 V-10, 5R110W 5-speed automatic and 264,000 miles shows no trouble codes.  This is a virtually rust-free Floridian ex-fleet vehicle (at least twice!), and I suspect its later years saw mistreated brakes (foot resting on pedal).  Otherwise, it seems mechanically sound (I've owned for 2 years, yet rarely driven). 

The front rotors are bad (glazed, yet true), the calipers are old rebuilds (thus marked during service) which I have re-greased, and the master cylinder may be original.  Upon purchase, I did replace the rear rotors because the right one was nearly disintegrated.  I also found the front left caliper sticking after driving, and after self-diagnosing (opening the bleeder valve released it), all calipers were greased with hi-temp CRC synthetic (the slides were not pretty, but not deteriorated) and both front OEM flex hoses were replaced.  The system's fluid was also flushed out (by me) using homemade tube/plastic bottle set-up at each bleeder valve consecutively from furthest to nearest the master cylinder.  While there MAY be air in the system due to a fault of mine, it would be slight and is not noticed in braking action.  Note, the fluid was VERY bad.  Nearly black and quite odorous.  The brakes now worked without issue.

Shortly after buying the van and doing above work, I did manage to tow a 10,000 pound trailer 1,000 miles (FL to TN) without brake trouble.  Now, over a year later (again, rarely used van.  Driven maybe once a month, 20-40 miles), I came across the front left caliper dragging again.  Knowing that the rotors AND calipers would probably best be replaced (but money being an issue), I chose to experiment and replace the 60-70% worn pads (only) to see what happened.  I used high quality exact-fit pads and was sure to level the fluid in master cylinder reservoir.  Well, here's the reason for my question to you...

First test drive saw the front left dragging again.  (The dragging begins after some time/brake use.  Perhaps 5~10 minutes/a couple applications.)  I parked it and chose to drive it again a month later.  However, I removed the ABS fuses (5 & 60 amp) to see if any change was noted.  This time, the RIGHT front caliper began dragging (and pulling, of course) and I was inclined to pull over while nearly to house.  The RF brake assembly smoked for a couple of minutes as it sat.  I got it back after a 30 minute cool down. 

So, while the van has the weak points I've mentioned, I'd like to find out what the immediate cause of trouble is.  I can add these notes: 

  The brake fluid is again fairly dirty-looking.  My 2-years ago process likely replaced all of the fluid, but in that time and only maybe 2,000 miles, it looks dark/bit smelly again.  Maybe that's normal.  Don't know;

  lifting each wheel to turn and check for cold drag (unheated), the left front showed some resistance, and the left rear as well.  The right front however (the last to be a problem) spun freely; 

  at least once, I have heard the hissing sound of the vacuum-power brake booster while in the driver's seat.  It certainly is not a regular occurance; 

  there are no leaks/loss of reservoir fluid.

I'm simply confused, even after looking up lots of DIY info online and tips as to symptoms/causes.  Realizing it could surely use a $500~$700 (my DIY cost) brake overhaul, I'd like to know what the immediate problem is.  Can it be AIR in the lines?  Might a worn/dirty master cylinder behave thus?  Could a poorly operating power brake booster cause slight brake application?  Even with ABS disengaged, can the pump or proportioning valve (does this have a separate proportioning valve?) cause such issues as alternating brake drag? 

Simply, I'm more old-school-oriented regarding cars.  I just don't know the possible complexities of this van's braking system.  As for ABS being unplugged, I've the same set-up on my Toyota Yaris for years.  I haven't a desire for ABS is all.  Used to old cars.  If I could completely bypass it, good.

If I can fix this issue of dragging, I'd at least feel comfortable driving the van again.  Then, I'll probably splurge for new goodies all around -knowing they need it, regardless of their sufficient functioning.

THANK YOU for reading all of this (if you did).  Otherwise, I don't blame you at all.