A very odd clutch problem I haven't seen before...

So my neighbor has an older Nissan Frontier that he assumed has the clutch slave cylinder failed. Apparently it's something that happens a lot, roughly ever 60k miles. He replaced it and asked me to help him bleed it.

If you lightly touch the clutch pedal it power dive bombs to the firewall with a lot of force. You can lift it fairly easily but a little pressure slams it down as far as it'll go 

Never had that happen before, if a slave cylinder goes out it just won't shift. Is this weird? Never had his problem before

It must have an over-center spring on the pedal and a lot of air in the system.

That's fairly common--just an over-center and air in the system, as Pete said. It should go away after bleeding, but don't slam the pedal down (move it with your hand) just to avoid damaging the master. 

In reply to Tom Suddard :

Good to know, apparently I haven't done enough slave cylinders before lol