I took the 2001 M-gator for a spin the other day and it overheated and shut down. It has the Yanmar diesel engine. I found the water pump wasn't moving coolant. Come to find out, if it sucks in air (like opening the radiator cap 
) it will lose the prime in the water pump and not pump water thru the radiator. I replaced the thermostat, radiator cap, and reservoir cap. I bled the system per the TM (P.I.A.). Anyway, I checked the radiator fan by crossing the wires and it runs. I ran the gator the other day and I feel pressure in the top hose (seems it's pumping), but the fan doesn't go on. I didn't run it too long as I don't want to overheat it again. I'm not sure when the fan kicks on so I'm not sure how else to check that it's functioning correctly. I've read NOT to open the radiator cap as this will suck in air (which I have already and learned the hard way). Anyway, I have a new radiator thermostat and, before I replace it (it's a bit of work), I would like to know how else I can test if it is or isn't the radiator thermostat. Any coaching?
) it will lose the prime in the water pump and not pump water thru the radiator. I replaced the thermostat, radiator cap, and reservoir cap. I bled the system per the TM (P.I.A.). Anyway, I checked the radiator fan by crossing the wires and it runs. I ran the gator the other day and I feel pressure in the top hose (seems it's pumping), but the fan doesn't go on. I didn't run it too long as I don't want to overheat it again. I'm not sure when the fan kicks on so I'm not sure how else to check that it's functioning correctly. I've read NOT to open the radiator cap as this will suck in air (which I have already and learned the hard way). Anyway, I have a new radiator thermostat and, before I replace it (it's a bit of work), I would like to know how else I can test if it is or isn't the radiator thermostat. Any coaching?