[Richard]

There are independent loops. One goes to the heater core up front. The other circulates through the AH boiler.

Great idea on figuring out the valves. I hope you remembered or labeled correctly.

So I can imagine one of two things. The first, and let’s do simple first. Is there any chance you used pink coolant in the Aquahot? Like Camco boiler fluid? Or even the pink Propylene Glycol normally used as ‘safe
‘ antifreeze. I do not recommend you tasting it, although a micro drop on your finger will not kill you. Ethylene glycol, the engine coolant is a sickly sweet taste. Propylene glycol, the Camco and safe antifreeze stuff, is slightly bitter.

The second is more insidious, and far fetched. The piping that the engine coolant circulates inside the AH boiler has failed. That allows the red coolant from the engine to enter the boiler. This would be no bueno.

What I don’t understand is if you closed the correct valves why the AH was not hot from the days drive. Keep an eye on the AH temp next time you drive.


Here is a bass ackwards way of checking the coolant loop between the AH and the engine. With the AH hot, electric or diesel, flip on the engine preheat switch and wait about an hour. Now go back and see if the manifold with the valves has hot pipes.