91 E-350 Brake problems 7.3 diesel

Background:
1991 Ford E-350 auto 7.3 diesel
Purchased used with 115k

Problem:
Brake pedal is very hard to push when first started. Then pedal goes to the floor after motor is running. Brakes are not very responsive.
Impossible to stop in a hurry, but does stop after pumping.

Things replaced:
Vacum pump pulling between 12 and 13 psi
Master Cyclinder
All Fluid from Master to brake components.
Rear wheel cyclinders both sides, shoes and drums.

At this point I am a little stomped, if the rear drums are not adjusted correctly to the point that the drum falls off would that cause this. I am going to tighten them up tomorrow night. I think the problem is air but I can't for the life of me find the leak.

Any ideas would be great.

Look at the hoses to the front calipers watch each one as somebody pushes the brakes. If you notice a bulge in the hose replace it. Look at the calipers for leakage and make sure the bleed screw is on top. This traps air in the caliper and you can't get them bleed. Use a flashlight and trace all brake lines looking for a damp spot. Does this have a hydraulic assist or a vacuum booster for the brakes. A leaking vacuum booster will cause problems. Is your vacuum pump for this purpose. Is the vacuum pump pulling 13 in vac or putting out 13psi a big difference.

The system uses a vacum pump mounted on top of the motor that connect to the brake booster.

I will look at the lines tonight when I get home.

Curious though I was able to bleed the brakes and get a continuous stream from each wheel cyclinder. Is it still possible to have air in the system?


Look at the hoses to the front calipers watch each one as somebody pushes the brakes. If you notice a bulge in the hose replace it. Look at the calipers for leakage and make sure the bleed screw is on top. This traps air in the caliper and you can't get them bleed. Use a flashlight and trace all brake lines looking for a damp spot. Does this have a hydraulic assist or a vacuum booster for the brakes. A leaking vacuum booster will cause problems. Is your vacuum pump for this purpose. Is the vacuum pump pulling 13 in vac or putting out 13psi a big difference.

I was working on my sons car years ago it was late and I was tired. The parts store labeled the front calipers as to sides. I put them on and got fluid through all bleed screws. Couldn't get the air out. It was observed that the bleed screws were on the bottom. Switched calipers to the correct side and they bleed out properly. So it is definately possible.
If you have a rubber hose from the vacuum pump to the vacuum booster put your vacuum gage in the line. Pinch off near the vacuum booster you might have a leaking vacuum diaphram.
When I lived in Ohio I had brake lines rusted through frequently. In Georgia where I live now I never observe it except on cars from people who moved south.