So....
Do you have to start the tractor to remove the loader?
OP is good, but more food for thought:
1) Don't drag racers and multi-engine pulling "tractors" often run dry blocks? Massive horsepower and rpms for 300 feet or 1/4 mile plus. (2+ minutes total run time?)
2) What is standard operating temp on a tractor, compared to the temperature thermostat opens at? If knowing how long it takes engine to get to normal temp, doesn't this give you an idea on how long engine runs without even opening the thermostat (basically the same situation if you clamp the hose)?