I have had problems with my Applause overheating since I bought it 6 months ago. Having had a trawl around the net I realised that it was a very common problem. I have looked at everything, and finally seem to have sorted it: The car would be fine for miles but would suddenly boil up and eject water from the expansion bottle, even though the temp gauge was still in the acceptable area. The gauge would then climb up to the top. The thermostat was obviously fine as it warmed up quickly to midway and then never moved. I finally sussed that the timing was way too advanced- it seems as if someone had timed it to the marks with the vacuum hose still attached to the distributor. It wasn't clear from the manual if one or both of the vacuum pipes should be disconnected and plugged, but I marked both positions on the dis body. One effect of this was to put the dis back into the middle of it's slot adjustment (a sure indication). I also found that the heater was completely blocked. I attempted to remove the core but needed to borrow the 'Jaws of Life' from the local fire crew. I finally made up a hosepipe connection and left it on tap pressure to one inlet for a while. Eventually a dribble of water came out of the other pipe. I then swapped the hose over to the other connection, and repeated a few times. It finally blew clear! The overheat problem has not shown itself since plus the heater works a million percent better.
This motor was originally made for a 'fore and aft' installation. When it was turned across-ways for the Applause, I think that the routing of the hoses for the rad are less than ideal. Lord knows how you change the thermostat- I think a trained ferret with LED light would be needed!