Zero coolant loss is the norm, anything else and you need to track & fix.
There should be a set of isolation valves between the engine & your hot water
tank. If there isn't, then install them - and close them. If the leak stops, then it's likely the hot water coil - if not, you know it's within the engine circuit.
- Should always have isolation vales on auxiliary loops like hot water tank, or cabin
heaters so you can close them and keep engine running despite hose/coil failures.
If there's no obvious coolant in the bilge
, then I'd put money
on your heat exchanger
. Pull it and take it to a radiator shop to get pressure tested. looking for bad gaskets as you remove.
Next most likely is a head gasket
- at least you'll have the heat exchanger out of the way.....