Gremlin Strikes Back

The coolant bypass valve arrived yesterday (thanks, autopartsway.ca... cheaper than eeuroparts too!). Naturally, the gremlin decided to take it up a notch, and the clutch pedal went limp and mushy. Again. Double-clutching helps with shifts, and so does pumping the pedal, but it's getting worse. Could it be the slave? Can't spot any external fluid leaks...