Truck Repair: Brakes, brake fluid reservoir, air pockets

Question
I have a 87 ford F150 4/4 6 cyl pickup.I stepped on the brakes and it just hit bottom with about 85-90% of brakes gone.It does not appear to be leaking at the wheels or in the line that I can see.The brake fluid reservoir seems to be full.My feeling is the master brake cyl needs to be overhauled or replaced.How do you do it or maybe its something else.Your help would be greatly appreciated Van. Thank you for your time and consideration.

Answer
Hi Dave,
I think you diagnosed it correctly.
The best way is to get a rebuilt, or new master cyl from a parts house.
Probably about $35.
Be sure to bench bleed it as the instructions with it should say.
Ask if a bench bleed kit is included. It is just a couple small hoses and plastic fittings so you can put fluid into the reservoir, and then using a screwdriver, pump fluid through them back into the reservoir, removing air pockets from the cylinder before installation.

Good luck,
Van