Brake pedal fades to HARD

[hp383]

Hey guys, Im trying to decide if this is a vacuum issue (as in bad vacuum pump) or if it is a brake booster failure.

When I approach a stop, I have normal pedal for about the first half of the stop, then you can feel the pedal get hard underfoot, and then you are left stopping with no assist, and fighting the pedal.

This happend quite suddenly, fine earlier in the drive, then later had this issue. This issue has been present ever since.

I cannot see any vacuum leaks (nor hear any hissing), have a new tree in the booster, new line to the rest.

I did notice about 3 weeks ago that my cruise control would slowly accelerate constantly, but thought that may have been related to the potentiometer modification that I had hooked up earlier that same day.

AC and heat controls still seem to be working fine, vents open and close as they should. Haven't tried the 4x4 in a couple weeks (just used it when moving over the 4th weekend), but I don't think the 93 uses the CAD or vacuum for engagement correct?

Dollar wise I'm hoping its a simple fix. Any way to test the vacuum pump itself?

[oldestof11]

The vacuum pump might be going out. Losing vac. Check for leaks behind the dash too.

The 4x4 is direct shift, no vacuum crap.