RE: IML: thermostats
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RE: IML: thermostats



I was also going to chime in on this but Fred beat me to it with my exact reply.  But to add a little more, installing a cooler thermostat does not necessarily mean the engine will run cooler.  A normal factory size radiator is designed to transfer just so much heat to the surrounding atmosphere.  To accomplish that, the water must remain in the radiator for a minimum amount of time.  A cooler stat will open fully at a lower temperature and cause the coolant to flow at a faster rate.  The factory stat will cycle the amount of opening during normal operations and cause the coolant to speed up and slow down.  This allows the coolant to stay in the radiator long enough to transfer more heat.  The faster flow rate will send coolant back to the engine before it has suffiecently transferred all the acquired heat to the atmosphere.  I’ve seen several people remove the stat completely and then scratch their heads wondering why the engine still overheated.

 

Basic rule of thumb, if you want a cooler running engine, you need a cooler stat AND an oversize radiator.

 

Both my Imperials have oversize cooling capacity with factory size stats.  They both run cool in all weather conditions. (and I never turn off the AC)  Both are set at factory timing specs.  I run premium fuel with lead additives in every other tank-full.  Both engines have right at 100k miles on them.  No pinging and no abnormal behavior.

 

Ken

67 Crown 4 Dr Ht

68 LeBaron 4 Dr Ht

 

 

From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Frederick Joslin
Sent: Wednesday, October 24, 2007 7:40 PM
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: IML: thermostats

 

I have to put my 2.5 cents (with inflation) about thermostats.

A thermostat is designed to get an engine above the thermostat setting quickly and to keep it there. The radiator keeps the engine cool. This is not a function of the thermostat. If you have excess cooling capacity in the radiator, the engine should run close to the thermostat temperature. The thermostat keeps the temp above its set point and the radiator has the capacity to drop the temp below that point so it should cycle around the thermostat temp. 

However, if the engine puts out more heat than the radiator can transfer to the environment then the temperature will increase until the heat produced is balanced by the heat shed.

Note that as the radiator gets hotter relative to the environment (air temp) the heat transfer becomes more effective since the rate of heat transfer is proportional to the temperature difference. Conversely as the air temp gets hotter (Arizona in the Summer) the effectiveness of the radiator decreases because the temperature difference is less.

Heat is generated in the engine and is transferred to the coolant which is shed through the radiator. It is the temp in the engine that we care about and there are two transfer locations; the heads/block and the radiator. Really three locations since in the radiator the heat is transferred to the radiator metal which is then transferred to the air. All of the transfer locations need to work effectively for a good cooling system. If you have poor heat transfer in the heads/block to the coolant you risk pre-detonation and potentially other issues regardless of how well the other parts work.  

 .       

Fred Joslin

 



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