Pilothouse Heaters

[grey beard]

Been workiing on my Model 61 Dodge truck heater, and have learned a few things in the process.

1. The heater hose from the water pump is the pressure feed to the heater and should be connected to the (surprise!) LOWER heater outlet. This forces air out of the heater as it circulates and gives you full useable heater core area. Most engine compartment pics I have seen show the water pump connection hooked to the topmost - or outboard - heater core fitting. This can allow air to remain in the heater core - works just like cutting the heater core area in half. This air will probably be expelled eventually, but unless you can bleed the heater circuit you would not be certain of this.

2. The much-touted fresh auir duct and fittings for Pilothouse heaters requires a rectangular mask to be fitted inside the firewall between the heater core and the firewall insulation. Without this mask or metal piece, air would enter behind the heater and escape into the cab without being heated. Having the fresh air duct and pickup funnel connected without this pieece is not logical. I have seen only one of these mask pieces in my life. They are even more unusual and difficult to find than the fresh air ductwork.

3. At least four different heater models were used in B series Dodge trucks. The most common type I have seen is the model 61. A larger unit called a Truckmaster was also used and appears to be the high end type.

If anyone can add to this information, I'd be grateful for the information. Needless to say, I'm also looking for the rectangular mask used in the fresh air systems.

Thanks

[Don Coatney]

Dave;

Are you sure about the direction of the water flow through the engine? I believe the flow would be from the back of the head through the heater core and returning to the suction side of the water pump.

The water pump pulls cool water from the bottom of the radiator and pushes it through the water distribution tube, engine water jacket, head, thermostat, and then pushes the hot water back to the top of the radiator. Would make no sence to push the cooled water from the bottom of the radiator directly to the heater core.

[Reg Evans]

Several winters ago I was wondering why my heater didn't seem to be putting out that much heat so I took a core reading with my infrared thermometer. I read in the mid 140's and my thermostat was a 160 degree. So....I though Ah Ha !!! I have the hoses hooked up wrong so I reversed them and took another reading. Crap !!! no real difference.

Please...don't shoot the messenger.

[grey beard]

If it were possible to remove both heater hoses at the heater core ends and hold the two hoses level, then rev up a warmed up engine with the thermostat already open, I believe you would discover that the greater pressure is coming from the water pump, pushing the hottest water inside the engine back ouit to the radiator top tank.Logic says both sources will be warm, but the hottest water in the engine is that which is on uis wa out of the block to the radiator.

Your thinking is correct that the water pump pulls liquid into the block through the lower radiator hose. It is for this reaspn that many vehicles use a bottom radiator hose with a spring inside to keep it from collapsing due to this suction. It is also true that the pump pushes water out of the block and into the radiator top tank. This water that is exiting the block is the warmest coolant inside the block during normal circulation. That's the stuff I want going into my heater this winter. JMHO:)

[Don Coatney]

Does there not need to be a pressure differential in order for water to flow? If the water pump is pushing water into the block and into the heater core at the same time where is the pressure differential?

[norrism1]

The fact is the heater inlet hose is from the back (top) of the head, hot water direct from the engine. The return hose goes to the water pump, that is how the circulation is meant to be. It is a continuios loop from back of engine to the front.

[grey beard]

Any of you gents ever start an engine with the thermostat open and the top radiator hose off? What force is it that pushes coolant more than a foot in height from the engine block to the top radiator tanjk under considerable volume and pressure? That pump force is greater than any at the top rear of the cylinder head, IMHO

When I think about this a little, we;re not debating rocket science here. Every one of us has the ability to pull two heater hoses and visibly SEE which side has more pressure. We're not guessing how many angels can dance on the head of a pin or some other esoteric theological phenominum . Check it out.

Over the past many years, I have plumbed many hot water heaters for tractor and snow removal cabs. The closer you can get to the top radiator hose and;or water pujp for the hot water source, the finer the heater operation will be, from my experience. The return heater line can exit into the water jacket anywhere - like the top of the cylinder head. Works just fine every time.

[grey beard]

On third toughht, hot water heaters will work when plumbed either way - as proven by the many Pilothouse trucks hooied up wrog. It's sorta like primary ignition coil wiring. They will work when hooked up backwards, but just not quite as well. JMHO

[Don Coatney]

Any of you gents ever start an engine with the thermostat open and the top radiator hose off? What force is it that pushes coolant more than a foot in height from the engine block to the top radiator tanjk under considerable volume and pressure? That pump force is greater than any at the top rear of the cylinder head, IMHO

When I think about this a little, we;re not debating rocket science here. Every one of us has the ability to pull two heater hoses and visibly SEE which side has more pressure. We're not guessing how many angels can dance on the head of a pin or some other esoteric theological phenominum . Check it out.

Over the past many years, I have plumbed many hot water heaters for tractor and snow removal cabs. The closer you can get to the top radiator hose and;or water pujp for the hot water source, the finer the heater operation will be, from my experience. The return heater line can exit into the water jacket anywhere - like the top of the cylinder head. Works just fine every time.

Dave;

I think you are wrong. Yes water will squirt out of the thermostat hole because that is the discharge side of the water pump. The connection located on top of the water pump is the suction side.

[bkahler]

2. The much-touted fresh auir duct and fittings for Pilothouse heaters requires a rectangular mask to be fitted inside the firewall between the heater core and the firewall insulation. Without this mask or metal piece, air would enter behind the heater and escape into the cab without being heated. Having the fresh air duct and pickup funnel connected without this pieece is not logical. I have seen only one of these mask pieces in my life. They are even more unusual and difficult to find than the fresh air ductwork.

Dave,

I'm one of the fortunate ones in that my heater came with the rectangular duct that goes between the heater and the firewall. I hadn't realized they were so rare. One of these days I'll have to check out my favorite junk yard in Nebraska and see if there are any in the parts trucks there.

Brad

[grey beard]

Well Don, you may be right. After looking at Merle's water pump pics I must agree that the pump inlet and the pump heater hose cpmmectopm appear to be into the same passage. What still befuddles me is that my own engine - external bypass system - has the pump heater hose fitting and bypass going right into the top hose area - a little different than Merle's photo. I have both the early and late style pumps here as well, for comparison. I'll try to loiok them both over again.

If I led anyone astray with wrong information, I appologize.