I'm changing out the coolant (from standard green Ethylene Glycol to CAT ELC) this week. According to the Beaver manual, my coach holds 16 gallons.
I drained the coolant and removed the thermostat (CAT calls it a Regulator). Then refilled with tap water and ran at 900-1000 rpm for about an hour. This got coolant temp up to 125F. Then I drained that, and repeated twice more, until coolant was draining out was clear.
Next I added a gallon of CAT Cooling System Cleaner and tap water and ran the engine for another 90 minutes. Temp is getting to around 125F (since thermostat is removed I can't get coolant as hot - but I know water is fully circulating through the engine and cooling system). I drained that out last night. Tonight I finish up the job.
Today I will run full "distilled water" in the system and then drain that out. Then I will add the final mix of distilled water and ELC.
So my question: I tried heating the coolant with the Aqua Hot Engine Preheat feature. The diesel burner ignites and circulation pump runs but after about 15 minutes or so the burner shuts off. Aqua Hat manual says to "run for about an hour and half". The circulation pump keeps running. Engine temp did not get above 125F.
Is this the way it is supposed to work? Outside air temp was in the low 70's. Maybe the Preheat only slightly warms the engine - and is not intended bring coolant temp all the way up to operating temperature (180+F).
Lastly, My Complaint -- The way Beaver installed the coolant surge tank is frustrating, one can not pour any coolant or water (from container or with a funnel). The tank cap is too close to the body - so you have to drop the Surge tank in order to add any fluids. To drop the surge tank you have to remove the air intake tube (so then you cant start engine).
I suppose to just top off the reservoir you could use a hand-held suction pump device, but not very practical for anything over a gallon. Now I feel better.