Problem with heat exchanger outflow

[DeepFrz]

Zee, the clogged passages will be in the raw water side so wont affect flow in the coolant side. Could cause the engine to run hot though as could a partial clog in the injector elbow after the heat exchanger.

[Stu Jackson]

The lines from the engine to the hwh should be from below the thermostat and the top of the coolant pump. Not in any line to the HX.

[donradcliffe]

Its fairly common for the heater loop not to work unless it is properly bled. Pull the top hose at the engine (I assume the heater end is lower), and pour coolant in till it overflows, then reattach and fill the coolant reservoir.

[Strait Shooter]

Originally Posted by rolandcavanagh

My experience is that the hoses for the auxiliary devices (heater, hot water heater) come off below (before) the thermostat, and return to a lower pressure point on the block. I'd be looking for a plug in the original hot water heater, or a bad coolant pump, but as I once discovered on my GB, a badly installed hose (one with a plastic cap still on the fitting, one with the hose crushed into the fitting) is a possibility. I'd disconnect the hose starting at the pressure (top) fitting and start the engine briefly with my thumb over it and assess the pressure and flow, then work my way through the system.

That's what I did last night. I had another project I was working on (lavac installation), and decided to start the engine and see what I could see.

Both auxiliary hoses coming off the engine (you were right about the arrangement) got at first warm, and then hot. No heat in the hoses at the appliance end though. I then shut off the engine.

After thinking about it, I removed first one, and then the other auxiliary hose at the fan heater. I got nothing from the first one, but lo and behold, when I removed the second one I got a flow of hot water from the hose.....yay!

It was late, I was tired, and I called it quits for the night. After more reflection I believe you are correct. I think the water heater has blockage in it, do they fail like that often? I looked, but can't find any evidence of that yet.

I need to go back and reroute those aux hoses several different ways to confirm what's happening, but I believe now I can find the problem.

Thanks everyone for the help, I'll post an outcome as well.


John

[Jubilee39]

If your heaters are in parallel with line going to heat exchanger you wont get senough of a differential pressure to cause flow. I have had to add throttle valves to generate the d/p needed
Joe

[Strait Shooter]

Originally Posted by Jubilee39

If your heaters are in parallel with line going to heat exchanger you wont get senough of a differential pressure to cause flow. I have had to add throttle valves to generate the d/p needed
Joe

I have been wondering about that. Damn......

What's a throttle valve?

[DeepFrz]

Throttle Valve:

A control valve that regulates the variable amount of fluid that is supplied to another fluid component such as an actuator

In this case it would be the heater or water heater, not an actuator. It would be nice to see a diagram of what you did Jubilee39.

[rolandcavanagh]

I'd try blowing thru the hot water heater loop - disconnect both ends and give it a hoot - should flow freely (don't drink the green stuff...). If it isn't really easy, there is your blockage. You could then try connecting just the heater without the water heater loop and confirm that it makes heat.

I did one of these installations late last year, and did put ball valves at the tees where the water heater loop and heater loops split - two purposes, I wanted to be able to cut off the hot coolant to the heater core in summer, and I thought I might need to throttle one device or the other to balance heat usage (turned out everything got really hot anyway).

BTW, my engine heat exchanger is on a different loop (I think I interpreted that yours is one loop; engine => heater core => water heater => heat exchanger?)

Hoping to hear what you discovered.

-Roland