We used to run water injection in our race car's for that very reason. When we raced in the dirt, the rad would get caked with mud and the motor would get hot enough for pre-det.
When I started racing, I used a old 30lb. freon bottle of R-12 (RIP) I would fill it half with water and pressureized it. Ran a hose to a copper tube that I drilled a bunch of small holes mounted in from of the rad with a valve right by my seat.
When the motor would get hot..I'd hit the valve for a few second's and it would wash the mud off the screen in front of the rad and cool the air going in. Funny thing....when I first installed it...In the pit's I would leave the back hood off. Other driver's would always check your car out to see what you got. I would let them see it for a second and then rush over thier and cover it real fast...
They would alway's go crying to the officials that I had something illegal.
Just trying to play mind games with them...anything to grab an edge on them.