Overheating cured by adding thermostat

T

TJMack

Senior Member
This may be of value to someone else. I was having an issue with my 1929 sedan overheating. I was losing water but it wasn't obvious where it was going. After some investigation I found that it was going out the overflow tube in the radiator neck as I was driving. I found this by running the engine at a high idle and watching in the radiator neck. I could see it swirling around and going out the tube. It didn't do it at a normal idle speed.


I added a 160 degree thermostat to slow down the flow from the water pump and it worked like a charm. I realize my radiator may be partly plugged, but I don't really think it's too bad if it is. I didn't time it, but when I had both radiator hoses off I held my hand over the lower hole and filled the radiator then watched the water come out when I took my hand away. It gushed out and didn't appear to be restricted.


I bought the car in December and I don't know if the previous owner had the same issue or not. He hadn't driven it in years. I had one of the fan blades come off, so I replaced the water pump when I put the new fan on. Therefore I know the flow of the pump is right up to par.
 
Exactly the same problem and solution with my 1930. I believe the new pumps have TOO MUCH flow. Another solution might be to shave some off the WP impeller blades.
 
Putting the thermostat close to the bottom of the radiator hose helps. Hold it in place with another hose clamp so it doesn't work its way to the top.
 
Were you actually overheating?? Did you use any type of thermometer to check the temperature?
Sounds to me that you may have had your radiator very full and the water was being pushed out the overflow tube.
Many folks add water to the top only to have it pushed out the overflow tube.
As long as the tubes are covered with water you are fine.
 
There are more than a few who have tried reducing flow and also using thermostats, and it has worked for them. Personally, logically for me, I do not understand why it would work. So many theories for and against. But to coin a phrase t"he proof is in the pudding" There must be something to this. I do not want to start another big discussion on the subject, has been thoroughly discussed on the Barn in the past resulting in very strong opinions on each side. I am just going to accept it as a mystery to me, and keep the knowledge of it for use in possible troubleshooting.
 
This subject has been discussed many times. The takeaway is, a marginal cooling system can benefit from the restriction of the thermostat or cutting down impeller blades. However, the benefit is seen in reduced negative pressure in the engine block, making steam flashover less likely. The reduced flow though does create less turbulance, and turbulance is good for heat transfer. Much better solution is to get the cooling system up to snuff. Clean block and clean or replace radiator.
 
mfarley said:
So, if you put in the alternative crankshaft pulley, that would affect charge rate also, correct?
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Haven't ran the pulley with the original generator.Logic says it would,but George Riley found the pulley effective 80 some odd years ago,imagine they increased the charge rate to offset any issue.
 
eagle said:
This subject has been discussed many times. The takeaway is, a marginal cooling system can benefit from the restriction of the thermostat or cutting down impeller blades. However, the benefit is seen in reduced negative pressure in the engine block, making steam flashover less likely. The reduced flow though does create less turbulance, and turbulance is good for heat transfer. Much better solution is to get the cooling system up to snuff. Clean block and clean or replace radiator.
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As you say, any improvement by reducing the vanes on the impellor is counter intuitive. I understand how reduced pressure inthe block will hasten boiling but has anybody measured the pressure inthe block? I think the Model A water pump would best be described as high volume, low pressure which would mean that the reduction of pressure in the block is minimal.
Also agree that reducing the vanes is a stop gap for a system that needs attention.
Radiators vary enormously in efficiency. I have a friend who had his radiator recored with a modern core (and therefor working at 100% efficiency). While we travelled together, both towing camper trailers in temps in the mid 30s (mid 90s F), my car was on the edge of boiling constantly. He had a piece of cardboard covering the lower 1/2 of his. Prior to this, he had overheating problems where ever he went even without the trailer. Sometimes ya just gotta bight the bullet.
 
1crosscut said:
Were you actually overheating?? Did you use any type of thermometer to check the temperature?
Sounds to me that you may have had your radiator very full and the water was being pushed out the overflow tube.
Many folks add water to the top only to have it pushed out the overflow tube.
As long as the tubes are covered with water you are fine.
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It was definitely overheating when I ran it long enough to pump the water out the overflow tube and below the core. As I said, I could see it swirling around and going out when I ran the engine at fast idle. With the thermostat in place it doesn't do that. The thermostat sure worked for me, but I'm also sure it's not a panacea for everyone's issues.
 
Thermal Syphon with water pump assist. That is what you are dealing with.

As I have mentioned many times. Goggle, Rocky Mountain Model A Club Cooling System Presentation. It will tell you everything you need to know about this subject.

I think you need your radiator looked at, and maybe also you block cleaned.

Do yourself a favor, Goggle the presentation.
 
TJMack said:
It was definitely overheating when I ran it long enough to pump the water out the overflow tube and below the core. As I said, I could see it swirling around and going out when I ran the engine at fast idle. With the thermostat in place it doesn't do that. The thermostat sure worked for me, but I'm also sure it's not a panacea for everyone's issues.
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Your answer to overheating wasn’t really clear. Just because water is swirling and going out the overflow doesnt necessarily mean your overheating. Was the temperature 212° and was there steam?
My car pukes water to below the overflow (which can’t have any holes), and consistently only need a couple of cups more than 2 gallons. I don’t overheat.
 
Hi TJ,


If not already installed, install a coolant temperature gauge in the top coolant hose neck. Do not trust motometers. There is a possibility your issue will return as it gets into spring/summer temps. Keep an eye on the temp, repeated overheating is hard on the motor. You have a cooling system in unknown condition. A model A cooling system normally does not overheat if it is in tip top shape. This includes a motor/head with no rust/scale, and a good functioning radiator that is properly sized for the model A.
 
I was doing a little research on overheating and came across this post from four moths ago. I'd love to read the article:
"Cooling System Seminar by Andy Weideman, Feb 25, 2012, Rocky Mountain A’s http://www.rockymountainmodelaclub.org/Technical_Info/technical_info.html"
However their server is no longer active. Does anyone have a pdf of this or know where I can get it?
Thanks
 
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