Have been reading various Jaguar engine repair and training manuals and found some interesting data that I haven’t seen anywhere else before about thermostats.
Manual indicates on how thermostats should be tested and indicates temperatures at which thermostats should be fully open:
“In the pressurized environment of the cooling system an 82c thermostat is fully open at approximately 96c and an 88c one at 102c.”
More about thermostat testing:
“Another reason for thermostats being changed is incorrect testing. The two main thermostats in general use are those marked 82c and 88c. These figures indicate the temperature at which the thermostat “cracks” open. To test a thermostat, place it in cool water together with thermometer and raise the temperature slowly until the figure stamped on the thermostat is reached. HOLD THIS TEMPERATURE FOR TWO OR THREE MINUTES to allow time for the heat to penetrate the wax. After this period the thermostat will crack open approximately 0,08mm, which is hardly noticeable, so raise the temperature a further 5 to 10 deg., when the thermostat will be visibly open. Remember that when the thermostat is in engine it rarely opens more than 0,25mm.”