I don't think that Tom is saying that air CAN'T get into the ABS module. Only that it's quite unlikely. And, in that regard, I agree. I (personally) believe it's much more likely that air would get into the system well downstream of the ABS.

BUT...it is entirely possible that air *could* get into the ABS module. No doubt about that.

 

Air can definitely get into a RWABS I can vouch for that and bleeding the air from them has always fixed the soft pedal if the normal stuff doesn't work. But with the AWABS I can't say i've ever had to do this so maybe it different but the parts diagrams and Service manuals are surely not all lies? Dads 00 v10 will lock up the front tires with a very heavy foot, the back has ABS and the brake pedal doesn't go anywhere near the floor.

 

Little tid bit from
Ford F-250 Super Duty Review - Research New & Used Ford F-250 Super Duty Models | Edmunds
If you're looking for a used Ford F-250 Super Duty, there are a few year-by-year changes to be
aware of. In 2001, updates were made that included standard four-wheel ABS for all
trims, an available reverse parking sensor, heated seats for the Lariat and more power for the
Power Stroke engine. The following year brought a six-speed manual, new seats and the option of power-adjustable pedals.


Sean

 

What I am going by is the OP had the system drained for doing brake lines and who knows what else before that. There were plenty of opportunity for air to get in every nook and cranny available threwout the system.

He is experiencing problems that is typical to air in the system even though he has bleed the brakes numerous times.

I would say the one last step that hasn't been done yet would be to cycle the ABS and bleed again. That is unless the OP wants to continue to throw parts at the truck?

 

It's not me, but the folks who designed and built the trucks who said that.

 

Well, we are suspecting air in the HCU unit. According to the manual part you posted that means the OP should have to cycle the unit. Thanks Tom!

 

I've attached the workshop manual section on brake bleeding.