Bobcat uses a safety system call BICS, the door is tied into that system
There is a sensor on the door, check the wires they like to break or loose connection
The water pump is belt driven, make sure the belt has good tension with no squeaks on any pulley
There is a weap hole on the bottom of the pump, if you have coolant coming out of the hole the pump is no good
Another thing is remove the radiator cap and run the engine to see if you see it...
I'm like 95 percent positive that tank has a drain, I have flushed them in the past before but can't remember the exact location. Funny thing is the dealer told us we had to replace the tank as well this is why I remember this. I will check the diagram