1987 Toyota Pickup brakes

you can narrow it down by pumping up the brakes then hold steady pressure downwards if the brake pedal fades to the floor then it's a bad master cylinder, if the brake remains hard you could have air in the lines.

the pedal does not fade. how could the system get air in it with no leaks and its been 4 yrs since i last worked on the brakes? i can be sitting a light with good pedal let off and press again and it will go to the floor, just sometimes. but sometimes hit them and it goes to the floor the 1st time let off hit them again and good pedal again.

it sounds like you got a small leak, you did not mention in your original post that you remove the rear drums and check the wheel cylinders. If I were you I would start with bleeding. Doesn't cost anything but brake fluid.
Note: the brake bleeding order:
right rear
left rear
right front
left front wheels.

This should be done about once a year because the fluid is like a sponge and takes on water from the air via the reservoir. When the fluid gets to around 3% water it has a lower boiling point and you need to change it out because you don’t want it boiling when the brakes get hot. When the fluid boils it makes bubbles which can compress and then the brakes don’t work very well.