I have not checked the master cylinder or modulator yet (been too busy with work and school), but I will soon. My next guess is that maybe the hoses are bad (back by the axle) and are flexing

 

Not likely to be the hose, but worth a look. I've heard of that happening but in my day, it's always been something else. But if it's cracked, definitely replace it.

I don't know if this was suggested yet (I might have missed a reply or two) ...but did you fully remove the bleeder screws to make sure the little hole at the taper isn't partially blocked with crud or rust? It's common and worth checking before removing the hose. You can usually clean out by hand running the right sized drill bit in the holes (by hand again) to clean out the crud.

However, if you do pull off the hose or any part of the rear lines, I'd pull off the front line again and any unions and blow it all out, then blow it out in reverse. Not out of the relm of possibility that a piece of paper, crud or anything that was inside the brake line got caught up in a union. Not likely, but at this point you have to start narrowing down what it isn't.

Consider hooking a small line to the distribution box and bleeding from there w/o any rear lines. See what kind of pressure you get. Might need a helper to put their 'glove protected' thumb over the line when you let off the pedal to work up pressure (or maybe put a small valve on it).

 

I don't believe anything could be in the bleeders because they're brand new. But I believe the hoses could be original, so don't they commonly start "Balooning" after that much time?

 

I would be very surprised if these are causing your issue. Could they be reducing brake efficiency? Yes, but when you are bleeding your brakes you are relieving the pressure in the system so similar to letting a balloon go the brake fluid would still come out. Maybe a little slower but it would flow non the less. You would also be able to gravity bleed the brakes which is mostly the method I use when bleeding brake solo.

 

Well I had someone to pump the pedal for me, so I did the other way. I'm going to have to try bleeding them at the modulator to see if I've got pressure there.

 

Well I bled the rear lines up at the ABS modulator and it appears that we have good pressure there. The pedal didn't go down to the floor, but it definitely went down and fluid was coming out good. So I guess I need to keep bleeding it farther and farther back until I find where I'm losing pressure at

 

yup, keep working your way back

 

What can happen if the rubber hoses are old is they split inside, but not all the way through. this creates a thinner walled weak spot where the line will balloon slightly allowing fluid in. Over time it can get bigger and eventually create a little flap that acts like a valve and restricts flow.

 

you might want to save yourself a lot of time and use a pressure bleeder, they can be rent or made cheaply. I believe 04duxlr put one together using GARDEN PUMP SPRYER

 

Well I talked to the mechanic who did it about my issue, and he said he might have possibly crossed the lines when they went under the truck, so that might be restricting the flow.