|
|
Posted by Clint Dixon on Saturday, December 06, 2008 at 17:52:07 :
In Reply to: Re: Where should temp needle be on a 251 CID posted by Vaughn on Saturday, December 06, 2008 at 11:16:25 :
Your quote is true in part: "The thermostat regulates an ideal operating temperature for engine life and operating performance."
This ideal engine operating temperature is very narrow. A thermostat in conjunction of other key components of the cooling system to establish and maintain engine operating temperature within the ideal range by regulating the flow of coolant to the radiator based on the temperature of that coolant. The thermostat senses only engine coolant temperature. It does not sense ambient air temperature, nor does it adjust itself to compensate for ambient temperature in any way. A thermostat reacts in a predictable way only to the temperature of the engine coolant. It begins to open when coolant reaches a predetermined temperature, and it fully opens when coolant reaches a higher predetermined temperature. Once engine coolant falls below the higher predetermined temperature, the thermostat begins to close. Once engine coolant falls below the lower predetermined temperature, the thermostat closes fully.
Thus, the following quote from your original post is misleading: "The cooler the ambient temperature, the temperature of the engine will vary according to the thermostat. Use the ambient temperature as your guide for your engine temperature."
One should not expect their engine to operate outside that range of temperature ideal for most efficient performance even when the ambient temperature is at the extremes of 115 degrees above zero or 30 degrees below zero. If the engine operating temperature is not maintained within this ideal narrow range, even during extremes of ambient temperature, then the thermostat, or the combination of other components of the cooling system, is not operating properly.
The following is quoted from the Service Reference Book of the Master Technicians Service Conference session #156. Prepared by Chrysler Corporation:
"THE COOLING SYSTEM
One of the complaints most frequently heard during cold-weather operation is in relation to the engine cooling system and the performance of the car heater. Therefore, a review of some of the fundamentals of the cooling system may prove helpful.
Heat developed within the engine is converted to mechanical energy to operate the engine. Not all of the heat is used for that purpose, however. Some heat is given off through radiation, and some is carried away by the exhaust system. The balance of the heat not used to operate the engine is carried away by the cooling system. In other words, the cooling system is carefully designed to control the operating temperature of the engine for its most efficient performance, and to carry away the excess heat.
If the engine runs too cool, the fuel mixture won't burn completely. Some of it will find its way down the cylinder walls and into the crankcase where it dilutes the oil and helps to form acid. If the engine cooling system is not adequate to carry away the excess heat, the engine will run too hot. The coolant will boil, and engine damage may occur.
THERMOSTAT
The thermostat has a very important job to do. It must stay closed when the engine coolant is cold, permitting circulation of the coolant within the engine and thus provide a short warm-up period. Then, when the coolant has reached operating temperature, the thermostat must open and permit coolant circulation through the radiator. Starting with the 1960 models, all engines have a 180-degree thermostat as standard equipment. This means a permanent-type antifreeze must be used in the cooling system. If an owner wanted to use an alcohol-base antifreeze he would have to install a 160-degree thermostat.
Some technicians believe that different thermostats should be used for summer and winter operation, on the theory that overheating is less apt to occur in hot weather with a 160 degree thermostat.
This is not true. Engine cooling is just as effective with a 180-degree thermostat as with one which opens at 160 degrees. Therefore, changing thermostats twice a year is an unnecessary inconvenience and expense.
If abnormal conditions are encountered, and the coolant temperature rises above 180 degrees, the thermostat will be fully open regardless of whether it is a 160-degree or a 180-degree thermostat. This means the maximum cooling will take place with either thermostat, and the possibility of overheating is no greater with on than with the other."
I included the full text above from this particular section of the reference book because I believe the paragraphs discussing the types of antifreeze and the operation comparison between the two thermostats is relevant to the original question.
I believe the following quote from paragraph #2, and a later quote from paragraph #4, are key to my point: "In other words, the cooling system is carefully designed to control the operating temperature of the engine for its most efficient performance, and to carry away the excess heat." "The thermostat has a very important job to do. It must stay closed when the engine coolant is cold, permitting circulation of the coolant within the engine and thus provide a short warm-up period. Then, when the coolant has reached operating temperature, the thermostat must open and permit coolant circulation through the radiator."
Junior
Follow Ups: