2003 EB front brakes locking

[stilbo]

Both front brakes are locking up.
Jacked front end up no spin.
Cracked bleeder on them and built up pressure released. Spins freely.
Apply pedal 3-4 times locked again.
Okay... Without a guessing game...
I don't want to replace hoses, calipers, pads and rotors only to have them lock again..
I've worked on vehicles for forty-five years and normally I'd chalk this up to pistonsnot releasing fully or hoses shot.
But
Both sides at once ?!?
Makes me wonder if the ABS is FUBAR?
Shouldn't be the master cylinder as I'd see locking on rear brakes as well and they are free...
Again, don't want to play the guessing game and start throwing parts at it until I find the problem...
Anyone else encounter this both sides at once failure?
It only has 168,325 miles on it...
:-/

 

[Hamfisted]

Yeah if you crack the bleed screws and the pressure releases and the caliper pistons move freely I'd be looking farther upstream too. I understand you pumped the brake pedal with the ignition OFF and the front brakes still locked up right ? This would point to the master cylinder itself or front brake lines , rather than anything electrical like the ABS module or Stability Control module. The master cylinder is the common point for both front brakes. A new Motorcraft master cylinder is about $130 from Rock Auto. Worth a shot anyway.


-Mike


Expedition master cylinders from Rock Auto


ebay.com/2003-2004-Ford-Complete-Factory-Service-Manuals-Repair-Manual-OEM

 

[stilbo]

Mike,
Thanks..
I wanted to boost the master cylinder when I applied the brakes after bleeding them down so status was key on, engine running...
Wish I knew what the brake circuit looks like in diagram. I have factory manuals for Mustangs and Explorers but nothing for Expeditions and F150's.
The only thing that makes me doubt that it's the master cylinder is: Both front calipers lock but rears don't and a dual circuit brake system usually divides the master cylinder's output diagonally... At least most that I've worked on.
If I were keeping this Expi I'd just throw a lot of parts at it and keep driving it but I plan on selling it and buying a low mileage 2013 XLT from a friend.
It must know my plans.
Considering that the rotor temperature was 671 F on the RH and 580 F on the LH I might just have to replace rotors, calipers anyway so might as well throw a master cylinder in too (and hopefully not the hub bearings)...

 

[Hamfisted]

Yeah try it with the ignition in the OFF position and see if they still lock up. The factory service manual says the brake system is a simple front and rear split, no diagonal direction in this one. I'd probably start at the master cylinder if it does lock up with the key OFF. After that look at the condition of the lines leading to the front calipers. Even the factory service manual lacks a nice system layout diagram though.


-Mike



Ebay.com/2003-2004-Ford-Complete-Factory-Service-Manuals-Repair-Manual-OEM

 

[stilbo]

Wow! Thanks Mike!
I popped for rebuilt calipers, rotors, pads and hoses..
Everything was toast.
This thing lived in Michigan till four years ago and it's in Indiana now which ain't no better winter wise.
I disconnected both lines at the calipers (Thank you for the front rear circuit split info!) and douched the front circuit with a qaurt of fres fluid. Brown and milky is BAD.. Finally got clear juice..
Assembling front calipers now and there was a weird hairpin type of spring in the hardware kit that wasn't on the old calipers.
???????
Any idea where this spring goes?
Thanks again!
Gonna post a seperate post with photo in case you don't see this for a while.

 

[Hamfisted]

Ok sounds good. I think if you're going to all that trouble I'd get the new master cylinder as well. No sense in going to all that work and leaving the heart of the system out and suspect. Yeah I saw on your other post you already discovered it was the factory zero drag spring. Why some previous owner or shop left it out is a mystery. If the front was milky the rear probably isn't much better. Probably a good idea to pressure bleed the whole system so you know it's done right. Good luck with everything.


-Mike