I just happened to be looking around the AH compartment, and just by coincidence I discovered that the hose that connects the expansion tank to the fill/radiator cap had come loose at the cap. I had always just checked the level in the expansion tank, and it was always near the full line. After reconnecting the hose, and after a cycle or two, the level had dropped considerably. Might be something to check periodically.
Mike
Wow crazy that you post this now. I was opening mine over the weekend to do a coolant test. Good thing I did. The hose was brittle in the last few inches going into the auqahot. Broke right off when I touched it. Also the radiator cap rubber was pretty hard. Cut back the hose to where the rubber was in good shape and replaced the radiator cap.
LOL me too! Mine had already broke off I think when I was trying to put the cover back on the last time. The hose was extremely brittle all the way through to the expansion tank. I bought a quarter inch silicon hose from Amazon and put that in but it's just a temporary solution I think as it's a little too flexible. I could see it getting pinched off maybe. I love how the connector at the top of the aquahot is pointing towards the front of the coach which makes it pretty much inaccessible to my large hands. Had a heck of time getting it on.
Also I replace the radiator cap at the same time and was glad I did as the gasket was gone.
AH expansion hose and radiator cap were the first items I did myself. I wondered why my expansion tank was empty instead of being on the cold line then noticed the hose was very brittle. After further digging I opened the cap and stuck my finger down in the top of the boiler and couldn't reach any fluid. So about one gallon of ethylene glycol (2000 model 451) a new cap and hose, the levels now read as they should when hot and cold. The information on this forum is priceless! Thank you