Hello, I have a 1997 amtran. Just as all the rest of them I have overheating issues. When I check my antifreeze plastic reservoir there is none. And I remember having to put some water in a few times because I was afraid its running low on coolant.
Wonder if its good to check it when the engine is running?
I'm sure others with more knowledge will chime in here, but loss of coolant could be a number of things, some worse than others. There are a few great threads on the 444 cooling system here, I've gotten priceless info on them while doing my cooling system rebuild.
My overheating problems were: bad fan clutch, partially stuck thermostat, semi clogged radiator and a bypassed charge air cooler.
That coolant is going somewhere, the trick is figuring out where. Worst case it's going in the engine oil! Check your dipstick and make sure its nice and black in there... Then start up the bus and start looking for drips.
Of course, if you're actually overheating, your coolant will boil right out of your overflow bottle. That's what it's supposed to do, but overheating a T444E is how you kill them.