Could also have been a residual air bubble after the pump was done. They can float about for quite a while and can make the temp guage fluctuate. Mind you, the temp guage is not really measuring actual temperature all that directly. I have gone through several thermostats and sensors in the last seven years. But somewhere in the system there was always a slight leak. Either the pump seal was leaking, or the various little leaks coming out of pipe clamps or wherever. What is interesting though, is that when there are no leaks whatsoever, the temp guage sits dead square and never moves. If it moves even the slightest amount the system is not 100% sealed. And the aircon doesn't work properly either. If the guage drops to zero suddenly the system is leaking badly enough to lose pressure that it is trying to tell you to panic a bit. Which it does.
Temps to go over 110 degrees this week in sunny Melbourne for 4 days in a row this week. That'll test the old girl in a big way. We'll see...