Transfer function for diesel radiator cooling system


I am doing a work-based project for college; it is control and instrumentation subject. I am trying to create an additional cooling system for a generator diesel engine. The problem is that during the summertime the radiator getting blocked by pollen and gets overheated and shuts itself down.

I am trying to introduce an additional water spray system that would spray some water on the radiator to prevent the shutdown. So, when temperature reach 90 degrees water pumps starts, solenoid valve opens and water spays through the nozzle.

My aim is to mathematically model the system and then simulate it in MATLAB. However, I am struggling to get a transfer function for the system. Any suggestions how get around it?