Water is not hot after driving for over an hour

[beerob63]

I have a 36' 1990 Land Yacht, which I purchased in 2013. Suddenly after two years, the water no longer gets hot after driving as designed. There are no blown fuses, and the gas water heater works just fine. Anyone have any suggestions?

[masseyfarm]

The engine assist heated water tank temperature depends on the engine operating in a normal temperature range which should be well above 160*.

Most diesel engines will have adequate cooling systems to keep the engine within safe operating temperatures during all driving conditions. This means, that if you are not working the engine, it will generally want to run cold.

Proper thermostat operation is critical to keep your diesel engine temperatures in the safe zone so that the heat from the combustion process will clear away sludge and deposits that may be detrimental to long term engine life.

That said, the HWT engine assist depends on engine coolant temperatures, and water temperature. So, if you start out on a cold morning, and drive down the flat valley bottom, it may take an hour to get reasonably hot water in the HWT.

It you were to start your day on the west coast and head on up Steven's Pass, you will be able to stop and take that shower after a half hour or so.

The thermostat would be the first thing to question, if your engine coolant temperatures do not seem to be normal.

Most engines will have a valve near the engine to shut off water to the heater system. Check to make sure that is open.

And one other possibility? If you shut off the heater, your system may not allow the coolant to circulate through the HWT heat exchanger. The coolant has to be able to complete the circuit to do that job.

Dave

[jdalrymple]

As mentioned above, the heat for the water heater while driving is provided via the engine coolant.

If engine cooling system is operating correctly, I would suspect a collapsed or otherwise blocked heater line running from the engine compartment to the water heater.

This hose also supplies the auxiliary heater core with engine coolant. These do rot and fail over the years and can be blocked with crud.

Another possibility is a blocked heat exchanger tube within the water heater itself.


Regards,

JD

[masseyfarm]

The heat exchanger on these tanks is external, not internal. (this avoids any risk of contamination of your water system)

The exchanger is welded to the outside of the HWT.

I guess another possibility would be that this weld has failed from vibration?

You should be able to check this visually from the back side, where your bypass valves are located.

Dave

[beerob63]

Dave,

Thanks for the detailed response. My rig is equipped with a 454 vice diesel pusher. Engine temperature and coolant levels are fine (not overheating), however I have not changed the thermostat since purchasing in 2013. Also, could you be more specific regarding the water heater system valve you mentioned possibly located in the engine compartment. Thank you again for the feedback.

Bryan

[beerob63]

JD,

Thank you for the response. A friend and fellow RV'er stated the same possibility regarding a blocked line, I will attempt to locate and inspect. As I informed Dave, the rig runs perfectly, no overheating or leaks.

Bryan

[Wazbro]

They were talking about running cold (underheating).

If it was overheating you would have hot water faster then normal.

[lepmer]

Is this only on the diesel pushers or all Land Yachts?