Well, the main thing is to make sure the air slide is nice and clean/free..use some oil too. Here is a post that has some info from another site, but the info also fits your chassis. Note that the main concern is that the air shuts down completely when the coolant is up to temp. I would also make sure you are getting water circulation, so feel that the tower gets HOT ..if it just gets warm, then the problem can be coolant circulation. Read this and separate what fits your condition and this will also give you a better idea of the working of this unit. Once you have the air shutting off, I can walk you thru the mixture steps.
http://www.sl113.org/forums/topic.asp?TOPIC_ID=1386&whichpage=1&SearchTerms=thermostat%2Cbulb