Mine did that. but the pedal itself would come back up. I had a leaky slave cylinder. Can you pull the pedal up with your toe and pump it a few times to get pressure? I could pump mine and then it'd work for a bit. Drove 1.5 hours home like that. Almost ran into the jeep in front of me on the trail too. I replaced the cylinders and the hose.

87 Dodge Raider 5sp 2.6l no jet valves, Tuffpan
OME Dakar leaf springs + T-bar crank + 2" body lift (4" lift).
5500lb winch, Starion alternator, grp31 marine bat'
OBA (stock AC compressor)
33x12.5x15 Baja Claws or Wintermark extra load 235/75/15 M/S