Brakes soft after sitting a few years

[rball716]

Okay...so everyone's nightmare...Built the truck and it was great. Then I went fuel injection and had a major issue, bought a house, got married....truck went on the back burner for a few years.

The good news...I got it running again. It's an 81 shortbox and when I built it I replaced the mater cylinder, can't remember if I replaced the booster (but I replaced most things), new brake lines, new calipers in front and drums in back, brakes worked totally normal (normal enough to drag race it).

Now after sitting, The pedal goes almost to the floor before getting firm. Its not a "soft" pedal, its like pushing air out of a balloon for the first 3/4 of travel then firm. With the engine off it pumps up to firm higher up like you would expect.

I bled all 4 corners with new fluid and that seems fine. The fact that it pumps up firm with the engine off seems to indicate the booster is fine. Not sure what could be going on given the brakes were great before it was parked and nothing changed. My guess was the fluid, which is why i bled through all 4 corners.