Fresh Water Pump Direction?

[witzgall]

Hi all;

I replaced our hot water heater this weekend. It has an engine circuit. The water is not heating up. I think it is because of air in the lines, but I am also not sure if I hooked up the two lines correctly. So my question:

Does the water pump pump water TO or from the heat exchanger? I would think to but they are not labeled.

This is on a Volvo 2002 18hp diesel inboard.

Any tips on getting the air out?

Thanks in advance,

Chris

[Pblais]

The water pump pressurizes the water system directly from the tank. You usually have a fresh water strainer before the tank to protect the pump. The normal water pressure will move water into the tank as you draw hot water. Engine coolant needs to flow through the water water heater to heat the water. The flow of that coolant could be the problem assuming you have fresh water flowing as well. The water heater does not really do anything except hold the hot water until used.

[donradcliffe]

The engine coolant circulates through a coil of tubing in the hot water heater, so it really doesn't matter which way you hook it up. Pull the hose at the highest point and add water. You should be able to feel the hose get warm as the engine heats up--it gets warmest fastest where the coolant exits the engine.

[witzgall]

Hi Paul;

Yes, I realize the function of each circuit. I should clarify. There are two hoses running form the engine to the water heater. One is directly after the coolant pump. the other attaches to front-top of the engine. Coolant is flowing through the engine, but not through the lines going to and from the engine. They are hot at the engine connections, but not at the connections to the hot water heater.

The heater we replaced was working, but original, so I replaced it. It turns out it was COPPER!!! I could have kept it forever, but it sure looked old.

Chris

[senormechanico]

Under normal conditions, the coolant will flow through the lines as soon as the engine's thermostat starts to open. It could be a defective thermostat, gasket catching the thermostat, clogged lines, maybe a plug in the heater connectors that didn't get removed, etc.

Steve B.

[witzgall]

Would it be possible that the thermostat was not opening, and this was normal? Outside temps were ~80 degrees F, the seawater might be 75? and I ran the engine at idle for 30 minutes. This thought crossed my mind, but I just figured that the engine HAD to warm up in that time period. Maybe I am wrong?

Chris

[Chief Engineer]

You need to find out what the circulating pattern of your freshwater side is.

A volvo shop manual should show you this.