1988 B250 Ram Van / 318 ..So this morning I go out and out of nowhere the brakes nearly go to the floor, and the warn light is on after backing up a little then going forward. Checked the master cylinder and yes it was low so I topped it back off, but still same thing. The pedal acts like it wants to pump up but makes an airy sound. Is the master cylinder failure? I want to narrow it down before I get into unnecessary part swaps. I've learned already that approach gets costly. By the way I didn't try bleeding them yet. Should I try that first? Just wondering because prior to this morning they were fine.. baffled Oh and also I did check around wheel cylinders and on floorboard for brake fluid..nothing was wet..

Refill the master cylinder, and pump the brakes for a couple minutes. Then, look around under the van for the puddle. You likely popped a line somewhere.

If the rear brakes have shoes, it's possible to have reversed the front shoe with the rear one. On my '77 van they weren't interchangeable.

That will only change brake performance, not pedal height.

Wrong. With the shoes reversed my pedal darned near sank into the floor, lower than it has ever been.

That's an adjustment problem.

NO! It's an engagement problem and the shoes failed to engage sufficiently.

Erm, the shoes are the same shape, and the shoe with the smaller 'brake surface' goes in front, as they are self-energizing. Putting the shoes on backward just makes the rear brakes EXTREMELY effective.... and very difficult to modulate.

Well then maybe the shoes were insufficiently adjusted but nonetheless, the braking was c***. (stars are my own)

Thanks for the input everyone. I probably should mention that the rear brakes are fine. I am retired and have not had to replace them or the front disc pads for over 2 years. I drive very little these day, probably less than 30 miles a month most times..so they aren't hardly worn any. I am wondering now if just for that reason, maybe the seals in the master cylinder or perhaps the rear wheel ones may have just broke down because the van sits idle so much..