I have a 92 E250 with a 5.8l motor and it will not reach operating temp. Matter of fact it will barely make it into the "normal" range. Coolant temp sensor and thermostat were replaced twice and it's not a malfunctioning gauge because the heat that comes out the vents is barely warm as well.
All I can say is it's mighty strange. Any engine will create heat from the burning fuel even on the coldest day. I suppose you had your heater turned on full blast. That would take away some of the heat, but still not enough to keep the engine from reaching normal operating temperature with no circulation through the radiator.
Here's my suggestion: Remove the radiator cap before starting the engine, this will probably cause some mess from spilling over. Turn the heater off and start the engine. Carefully watch for circulation of the coolant while you let the engine idle for five minutes or so. You should get no circulation until the coolant gats close to 180*, but your heat is being dissipated somewhere.
One more thing to check: When your t-stat housing reaches the 117*, The coolant shouldn't be flowing through the radiator yet. So the coolant should be cool or cold to the touch. Also check all points of the radiator as well as the bottom radiator hose close to the radiator with your IR thermo.
trying to master the modern automobile,(truck too of course) good luck to me.
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