Lou Earle Posted November 2, 2006 Report Share Posted November 2, 2006 I got to thinking about the heater location of the return and intake hoses. Think About it. One hose is at the back of the block ant one of the furtherest points from the cool water from the radiator as is the temp Gage. Also, water returning to the radiator is forced up and into the radiator from what ? the cooler water( remember the water pump is connected to the lower radiator hose) being pushed thru the head by the pump. So does it make sense that the designers of the heater would have colder water going thru it or get water from the hot source and return it to the cooler? I am going to measure the temp on both hoses by hand and by the Lazar temp Gage. Which one you want to bet on is the return hose? I bet it is the one from heater to above water pump. Lou Quote Link to comment Share on other sites More sharing options...
BobT-47P15 Posted November 2, 2006 Report Share Posted November 2, 2006 Sounds logical Lou. And, of course the water shutoff valve is right there at the rear corner of the head to keep the hot water from flowing thru the heater. Click on link to view valve. http://img.photobucket.com/albums/v96/BobT3/Petey%20Plymouth%202/100_2349.jpg Quote Link to comment Share on other sites More sharing options...
Lou Earle Posted November 2, 2006 Author Report Share Posted November 2, 2006 Well the temp of the hose from the rear of the head to the heater is Hotter than the one leading from the heater to the water pump. Not a lot hotter but noticeably hotter. The lazar temp Gage is busted so could not do it.BUT take a look at the back of the water pump. Seems like the water pump pushes water down the distribution tube to the back where the original heater connection heater is located on the passenger side rear of the head . So that would indicate that the water at the rear of the head is the hot after going thru the dist tube. and be warm as it passes by the temp Gage. So I believe the water enters from the rear of the head to the heater and returns to the water pump. Also take a look at the rear of the water pump- the main outlet to the engine is thru the dist tube to the engine- makes sense- send the coolest water down the area with the most heat so the water can absorb it. That explains to me why the cut off is at the rear - it cuts off the hot water going into the heater. Maybe not all that important but I am glad to now know how the water circulates. Quote Link to comment Share on other sites More sharing options...
TodFitch Posted November 2, 2006 Report Share Posted November 2, 2006 Gee, I thought that was pretty obvious. You can tell just by looking at the water pump: The heater hose inlet passage goes to the inner diameter of the centrifugal pump blades (low pressure side) and the outlet of the pump is at or past the outer diameter of the pump blades (high pressure side). It might not be true on the bypass style thermostats but on blocks without that, like my 1933, the block and head are definitely under pressure before the thermostat opens and allows flow to the radiator. The time I lost a core/welsh/freeze plug was on wide open throttle when the engine was cold (thermostat closed). By the way, this is one thing that Ford got very wrong on the Model A and early V8 engines as those pumps pulled water from the engine. That meant that the water in the Ford engine is under less pressure than in a Mopar engine of the same vintage. That slight pressure difference does change the temperature at which coolant boils and gives Ford less margin. Of course running the exhaust through the engine on the V8 did not help matters. Nor putting the fuel pump at the back of the engine in the warmest part of the engine compartment. But then Ford was not known for engineering like Chrysler was. Quote Link to comment Share on other sites More sharing options...
Lou Earle Posted November 2, 2006 Author Report Share Posted November 2, 2006 I have several A models and one 48 Ford with a 53 mercury flathead .If the timing is any off they will overheat bad! I never knew why Fords did that and others did not . Thanks Tod. I posted my s"cientific findings " because soem in earlier postings thoughtthe water flowed from the water pump to the heater and then into the head. Rather than fron head to heater then to water pump Lou Quote Link to comment Share on other sites More sharing options...
grey beard Posted November 4, 2006 Report Share Posted November 4, 2006 Wellllll, now all y'all have really got my curiosity up. We all understand what the water does in the block and in the heater, and even which engine connection is supposed to feed the heater. My question is, which heater connection should be the inlet and which the outlet? My Dodge is a truck, and the heater has one connection considerably higher than the other. Should the hot water enter from the top or bottom? What say you, gentlemen? Dave Erb Quote Link to comment Share on other sites More sharing options...
Guest Nile Limbaugh Posted November 4, 2006 Report Share Posted November 4, 2006 I don't think it makes any difference which way the water flows through the heater. It won't be in there long enough to make any difference. Quote Link to comment Share on other sites More sharing options...
greg g Posted November 4, 2006 Report Share Posted November 4, 2006 I have a model 36 in my P 15. It has a sem semicircular exchanger about three inches thick, so the pipe fittings are level. As noted previously, flow is flow and and it really doesn't matter. But gravity is also gravity and it probably makes more sense if the core has upper and lower fittings, to plumb it inlet at the top outlet at the bottom. Quote Link to comment Share on other sites More sharing options...
Normspeed Posted November 4, 2006 Report Share Posted November 4, 2006 Not a P15 quirk, but on a Bronco forum a while back it was noted that if you reversed the heater connections at the firewall you could get some gurgling noises in the heater core. Quote Link to comment Share on other sites More sharing options...
TodFitch Posted November 4, 2006 Report Share Posted November 4, 2006 Not a P15 quirk, but on a Bronco forum a while back it was noted that if you reversed the heater connections at the firewall you could get some gurgling noises in the heater core. Sounds like there is some air in there that is not being purged by the flow of coolant. The semi-circular heater core mentioned in another response would be able to trap air too. On my 1930s vintage aftermarket heater there is a radiator drain tap type of fitting on the top of the heater. I use that to purge air from the heater core any time that I have drained the cooling system. I bet that semi-circular core has one too. Without it, I suspect your best bet would be to have the flow of coolant be from bottom to top so that it is more likely to carry any trapped air out of the core. If you can purge the air the I don't think the direction of flow will make much difference. Quote Link to comment Share on other sites More sharing options...
Guest wisconsinjimmy Posted November 5, 2006 Report Share Posted November 5, 2006 Well new to the site but in my opinion it really does not matter which way the water flows but if the hot is on the wrong side of the valve then the heater will tend to stay hot rather then cool. Every time this type of subject comes up It get people to scratching their scalp any who that is how I figure it. JimG in WI Quote Link to comment Share on other sites More sharing options...
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