Squishy brake pedal

[Mike Myers <mimyers@prairie.NoDak.edu>]

I have a problem with a squishy brake pedal.  I recently just finished
rebuilding my brake calipers, installing SS brake lines, and new parking
brake cables.  Bleed my brakes like I've always done before, using a
pressure bleeder.  The car is an early 89 200TQ.

However, if the car sits for a while, the first time I hit the brakes, the
pedal is very easy to push, after a couple of pumps, the pedal will get
progressively harder.  If I start the engine, the pedal will slowly go to
the floor if you keep pressure on it.

I know I don't have an external leak, I checked every connection multiple
times after stomping on the pedal for a bit.

I've bleed my brakes 3 times now, with absolutely no air the last time.

Am I looking at a internal leak in the master cylinder?
	-Mike