Water temperature

[Mitch//pa]

I fear that we may be shortening the life of our Model A engines by installing a thermostat within the circulating coolant system, especially when driving them in warmer weather. Here are the reasons why:

• The Model A does not have a bypass system as on more modern engines.
  
  • A bypass system bypasses the radiator but keeps coolant circulating through the block when the thermostat is closed.
• The Model A coolant flow depends primarily on the “Thermal - Siphon” effect, supplemented by a water pump at higher RPM.
  
  • The “effect” of the “Thermal – Siphon” effect is greatly reduced by any restrictions in the flow path, such a a thermostat.
• When the thermostat is open, it still presents a large restriction reducing coolant flow adjacent to the cylinder walls and head.
• Therefore, the bubbles attached to the water jacket due to boiling cannot be as readily carried away, resulting in localized overheating at the cylinder walls and valve seats.
  
  • It is desired to keep the oil film on the inside of cylinder walls under about 375 Deg F. Otherwise the oil film will begin to vaporize, resulting in increased upper cylinder wall wear. Also the valve seats will run hotter, resulting in shorter seat and valve life.
• Finally, the “Thermal – Siphon” effect already acts as a thermostat by increasing coolant flow as the coolant increases in temperature.

I would recommend a study of the seminar put out by Rocky Mountain A's entitled “What coolant to use”. The concept of “Nucleate Boiling” is discussed here. This phase change (in this case, water to steam) occurs at the jacket surfaces in any liquid cooled engine once a certain heat load is reached. This phase change cooling is similar to an air conditioning system in which the liquid freon flashes to gas in the evaporator, resulting in the absorption of heat). The bubbles which form on the jacket walls are carried away by the coolant flow where they later condense. New bubbles form, and the cycle continues.


Here is a link to the above seminar. I have read it, and (as a mechanical engineer) have found it basically sound.


http://rmaford.org/wp-content/blogs.dir/396/files/2012/01/Cooling_System_Fluids_v2007.pdf

the stats come with a bleed hole in them and recently someone posted one with 2 holes.. i make sure mine has 3 bleed holes.
shortening the engine life? i dont think so as it's all about water temperature and not running to hot.. a stat wont cause that

 

[Allanw]

If it runs too hot, you probably have a blocked radiator, thermostat or not!

 

[Mike V. Florida]

I fear that we may be shortening the life of our Model A engines by installing a thermostat within the circulating coolant system, especially when driving them in warmer weather. Here are the reasons why:

• The Model A does not have a bypass system as on more modern engines.
  
  • A bypass system bypasses the radiator but keeps coolant circulating through the block when the thermostat is closed.
• The Model A coolant flow depends primarily on the “Thermal - Siphon” effect, supplemented by a water pump at higher RPM.
  
  • The “effect” of the “Thermal – Siphon” effect is greatly reduced by any restrictions in the flow path, such a a thermostat.
• When the thermostat is open, it still presents a large restriction reducing coolant flow adjacent to the cylinder walls and head.
• Therefore, the bubbles attached to the water jacket due to boiling cannot be as readily carried away, resulting in localized overheating at the cylinder walls and valve seats.
  
  • It is desired to keep the oil film on the inside of cylinder walls under about 375 Deg F. Otherwise the oil film will begin to vaporize, resulting in increased upper cylinder wall wear. Also the valve seats will run hotter, resulting in shorter seat and valve life.
• Finally, the “Thermal – Siphon” effect already acts as a thermostat by increasing coolant flow as the coolant increases in temperature.

I would recommend a study of the seminar put out by Rocky Mountain A's entitled “What coolant to use”. The concept of “Nucleate Boiling” is discussed here. This phase change (in this case, water to steam) occurs at the jacket surfaces in any liquid cooled engine once a certain heat load is reached. This phase change cooling is similar to an air conditioning system in which the liquid freon flashes to gas in the evaporator, resulting in the absorption of heat). The bubbles which form on the jacket walls are carried away by the coolant flow where they later condense. New bubbles form, and the cycle continues.


Here is a link to the above seminar. I have read it, and (as a mechanical engineer) have found it basically sound.


http://rmaford.org/wp-content/blogs.dir/396/files/2012/01/Cooling_System_Fluids_v2007.pdf

Thirty-six pages but an interesting 36 pages. It makes a compelling argument against thermostats.

Are we applying conventional wisdom of modern engines to the engines of the 20-30's that were designed with the water pump only to help thermo syphon and not replace it?