[Richard]

On coach 390, there was a small pump located on the driver side of the engine that helped circulate coolant to the aquahot and to the dash heat.

I don't see that pump on 512. I can get the coolant to circulate to the AH while driving if I activate the engine preheat, which of course turns on a pump inside the AH.

My question is do you have the circulation pump by the engine? If you do, can you snap a pic so I can see what the make and model might be?

In cold weather driving, the engine preheat pump does not circulate enough volume to keep the AH or dash heat much above 120. I am thinking of adding this pump to 512.

[qcj]

Richard, My AH is always hot after driving. How the engine heat gets there I don't know but will check and see if there is a pump or something. I do not activate the engine preheat. The water temp. is never as hot as the engine temp. but is about 160-170 degrees.

[qcj]

Richard, My AH is always hot after driving. How the engine heat gets there I don't know but will check and see if there is a pump or something. I do not activate the engine preheat. The water temp. is never as hot as the engine temp. but is about 160-170 degrees.
I just figured that the engine water pump fed the water to the AH. Have you checked the four cut offs with the black handles that feed water to the AH and the dash heater?
I had to replace this set of 4 cut offs this last year.

[encantotom]

Chappell I need to replace them did you use a different kind of valve than original?

Tom

[qcj]

Tom, I ordered them from Newell which are the same as the original. I thought about replacing them with ball valves, but decided to go with the same ones . I think the top two go to the AH and the bottom two to the dash heater. I ran new hoses from the engine to the valves but not the long ones to the AH and heater. This way if I ever have leak I will be able to turn them off. The old valves leaked and could not stop it. I think they were about $160.00 each.

[Trainer]

Unless valved off, the main engine water pump always circulates engine coolant through the AH heater all the time the engine is running.

In temps below 50 to maybe 45 degrees F, the 3/4 inch hose can not transfer enough heat to keep up with the demand for interior heat. So in cold conditions, turn on the diesel burner.

[qcj]

Tom, the biggest reason for not using ball valves was that I was afraid that the heat and coolant would deteriorate the ball and seal. I went over to the NebCo factory here in town and they would not give me a good answer. That was the big reason for going with what Newell used.

[lbrachfe]

Newell uses a Monoblock design that can be found in many applications including home radiant heat systems. I'm sure that any 4 port with the same size inlet and outlet would serve as a fine replacement. The heated coolant needs to flow through 45' hoses to the front heater core and then return 45' to the engine compartment and that's a long way, but as others have posted after driving it's plenty hot from the engine circulation.
Richard, you may have a blockage or as was previously suggested you may have the valve turned down or closed on one of the four ports on the Monoblock... I cleaned and tightened it all up at the Newell Factory when my radiator was replaced and it was simple to do , but not the easiest place to get your hands around.

[bestgenman]

I remember reading in the AH manual that the circulating pump located beside the AH unit sends AH heated coolant to the engine and when the engine is running the coolant flow is reversed by the engine coolant pump. The manual instructs the user to turn off the AH circulating pump while the engine is running for optimum performance.

I also remember on my 89, there was a pump located in the front end near the back side of the headlight bucket to assist flow to the heater core. it was activated when the heat control was set for heat. If you were to install a pump, whether in the front or rear, in the loop to the heater core it certainly wouldn't hurt.

[qcj]

With 19 lbs. of pressure, why would one need a pump?