Imperial Cooling System Repair Information

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Special Service Tools Catalog - 1956, Miller Manufacturing Co.


How to tell if your engine is running too hot.  By Dick Benjamin

The proper temperature for an engine is different for different eras. Modern engines have 195 or so thermostats, so the coolant temperature inside the engine is often around 215 or 220 for normal operation. But these vehicles were designed to run that warm, for better pollution control and higher efficiency. They have pressurized cooling systems (15-18 PSI), coolant recovery tanks to recover the spillage after shutdown, and they run coolant with a boiling point of 255-265 degrees. The trip point for the idiot light on an '81 Imperial is 263F. Your old timer was designed to run much cooler, probably from 150 to 170, and very likely did not even have a thermostat when it was new. The cooling system is not pressurized, and was not intended to run anything but pure water, so your boiling point would be 212 at sea level, and maybe 200 at higher elevations. If the engine runs much cooler than 150, you were expected to partially block the radiator to keep the temperature up to the point where the oil would flow easily, and the crankcase would evaporate all the combustion products when the engine is up to operating temperature.

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