Bear with me on this one, I'm not a happy camper. I had soft brake pedal, and I replaced the master cylinder(it was leaking into the booster), as well as I replaced the booster assembly itself. Also replaced all rotors and new pads. When I went to bleed(Using a motive power bleeder at 15psi), I found that the brake caliper bleed screws were corroded and sheered off. SO what the hell I bought 4 new calipers too. While I was there what the hell I also installed 24 new wheel studs too........

I then proceed to bleed, the brakes are 50% better but still something is not right. Did some research online and states that the seals inside the ABS pump could be shot and cause this symptom.

I ordered a scanner that has ABS system scanning capability as well as the ability to bleed the ABS system and module; I still don't think that is the issue because the brake goes to the floor. A little air wouldn't cause that. That being said I'll still do a full ABS bleed to eliminate that as the issue.

I'm looking now at the possibility of replacing the ABS pump assembly, I found a video online that shows a way to possibly diagnose. Anyway, I can't find these things new and the used ones are ripped out of old trucks and have the ABS computer attached. I read that I have to have the dealer program that ECU to the truck's VIN/PCM so they talk properly.

1)Can I get the pump separate and just attach my ABS ECU and not worry about programming?
2)If I have to get an assembly, I assume I need to talk to a dealer now to see if they can do the program before I buy. Can I use one out of any year 04-08 F150 4x4? I have a 2006 5.4L FX4.

Any info on this replacement or diagnosis?

 

Theres quite a few videos on youtube for the earlier generation of F-150 showing how the pump can leak internally and cause what you are describing, but I don't see any for the the 04-08.
Here is a decent one on a van which shows some basics of troubleshooting.
I don't think the 04-08 has those caps to take off and test that way though, so basically since you've ruled everything else out its probably safe to assume its the abs pump, but if you could find some plugs for the master cylinder you might want to try plugging it and making sure its not the problem.
Fordtechmakuloco has a video on the like 06 taurus that shows they had problems with the ABS pump sticking valves inside so the pressure just loops around inside the abs unit instead of running out to the calipers so it seems entirely possible this could be your problem.

As far as replacing the pump, yes you can separate the electronics module from the pump portion there are 2-3 screws holding it on. If you reuse your electronics you don't need to worry about reprogramming anything to your truck but I think you want to try to stick as close to the same model year as possible to avoid any possible non compatibility.

 

Thanks man I appreciate the wealth of info. After I do the abs bleed this weekend I’ll start looking for a used ABS assembly from the same year as my truck. I see a lot on eBay for around $100.

thata great that I can separate the abs pump from the module.

Also I looked all around the assembly in my truck there are no test ports to be found.

 

hmmm, wish I knew how to verify the programming bit. I know us new edge mustang guys if we have the cobra brakes (99/01/03/04 cobra, 03/04 mach 1 and the bullet cars) all run the same module, we just buy used ones or have the computer fixed and sent back. Nobody does any programming.

The ABS computer module should only be a couple of screws, if you don't have a constant ABS light indicating an issue with the current module, I'd just swap them and hold onto the other as a spare

 

Yes my actual ABS module computer is working fine. If there is a failure it’s the actual seals in the ABS pump. No ABS codes or anything.

 

Ok so I did the ABS bleed procedure and I ran another 2 quarts of brake fluid through the system with the motive pressure bleeder.

still similar feel in pedal. What happens is there is not much resistance at the end of pedal travel and I can hit the mechanical stop of the pedal.

I took it out for a test drive and surprisingly it is driveable. I did some 50 to 0 stops, pedal is on the floor, but the front tires did chirp a little and it stopped on an acceptable distance. It’s still not right though, I compared the pedal feel to two other cars I have and it’s limp at the bottom. Very little resistance.

I think at a certain pressure the seals in the abs pump are leaking. I took off the master cylinder and there was no sign of fluid leakage after those hard stops. No other leaks anywhere else either.

Just an update.

 

I am not a fan of abs brakes ,i go back to when we pump the brakes ourselves manually . If I have trouble with the abs I will proceed to delete them . I want more info to do it but the heck if I want to spend big money fixing them . I learned to drive on snow etc , I see no need to give this system control .

 

Yeah well if this thing keeps giving me problems I might just have to do that.

I got one trick left I’m going to bleed the system AGAIN using the old school wife on the brake pedal method. Maybe the pressure bleed is somehow not getting every thing out without actuating all the pistons

 

.
np

 

You're not a fan of safely stopping ?

There is no way you can 'pump your brakes' out of hydroplaning.. because (wait for it) what you are doing is the EXACT SAME THING as the ABS module does.

Stop spreading nonsense. ABS and airbags are revolutionary safety advances.