Keith,
Some added info...... The mixing valve that Bob pointed out is under the burner and you can adjust that. If you find that it is frozen or the temp does not change it could be stuck with mineral deposits from use and there is a kit if that is the case. If your water flow is especially high that can be a factor.
If you have an IR gun you should see something a bit lower in temp then the 180, more like 160 + at the pipe leading to the radiator cap. If you are getting 160+ then the thermostats are probably working well. That temp is regulated by some button thermostats which can possibly need changing if the temp stays low.
Beyond the tube that comes from the overflow tank to the cap neck, which is a notorious leak point, the cap itself fails often.( BTW you can buy silicone hose on Ebay, I think it was 5/16ths and you will not have to worry about the overflow hose ever again). I replace my radiator cap every couple of years as a routine.
The solder joint between the copper or brass cap receiver and the boiler steel stand pipe is also a problem area, hopefully yours is fine. Beyond that there is evaporation, they say up to a quart a month but I find that a bit hard to believe. These systems stay hot all the time, as opposed to a car, and the evaporation rate rises dramatically with temperature so there is some of that going on.
Your coach is the same year as mine and this is likely to be the manual you need.
http://www.aquahot.com/eSource/ecom/eSource/staticpages/documents/AHE-100-04S130-04XAqua-HotOwnersManual09-29-04_002.pdfI have been working on my Aqua Hot since we bought the coach and there is "always something". If you find that you leak with the expansion tank up to level and the leaking problem is in the cap area or above you can run these systems with the boiler being full while hot and not driving fluid to the expansion tank. You just have to let it cool some once in awhile and open the cap to check it and replenish the main boiler until repairs can be made. I made a wooden dip stick and run the level about 2 inches below the cap when cooled, until my leak issue is resolved. Hope this helps.
Later Ed