Originally Posted by monte
Just an update on our water heater. It still seems to be overheating
, but only when it's heated from the engine
, not 220v. The pressure relieve valve is opening and releasing water into the bilge
and when using the hot water the first few litres is brown like rust...
I'll check if there's some sort of mixing valve that regulates the temperature
You said before that the heater is a Quick B3. I am familiar with those because I took two of them apart last week.
The mixing valve, if any, is irrelevant to your problem because it is downstream of the heater.
The thermostat that cuts the electric
heating is also irrelevant because you say the problem is when the engine runs.
IMHO most likely immediate root causes are
a) engine coolant
is too hot because engine thermostat is not working well, air lock, low coolant
b) pressure relief valve is defective.
c) combination of a) and air trapped in the top of the tank that expands a lot when the temperature increases from the electric
cutoff to the enginve coolant temperature). I have not looked in side this model but other models will let some air get trapped on top.
You can do the differential on the first two by measuring temperature of the hoses that take engine coolant into and out of the water heater. That is easy to do with an infrarred thermometer or a multimeter with temperature probe. If you will be in the BVI next week I can help you out.
Regarding the last one, check if the hose that takes hot water out of the heater goes uphill all the way to a tap somewhere (as it should). If yes, open that tap and let any air out. If not, you wil have to purge the air out.
I do not like the "rust" finding. AFAIK those Quick heaters have stainless tanks
(at least the ones I have worked on). Are you sure you are not losing engine coolant into the hot water through a puncture in the water heaterīs exchanger. Make sure you save a sample of that "rusty water" and compare the color to your coolantīs color..
By the way, if you want to take out teh heating element to see inside you will need a 55mm socket.... Only $5 from Amazon...
While you are at this check out if your heating element comes with a magnesium anode and if not check if it has the female M6 thread to insert an anode... The old ones donīt, and if you use shore water that is not RO product you may get corrosion