Here is an article from trailer Life Magazine about a spaying system for the radiator but I think they are out of business. It should not be too hard to make a system like this.
March 2001
Bidena's Desert SuperCooler offers a simple, yet effective approach to keeping your engine cool, even under the harshest towing conditions. A dash-mounted control unit periodically turns on the special Shurflo water pump, which dispenses a pre-measured amount of water through spray nozzles to the front of the engine's radiator. The company says this cooling spray increases the radiator's cooling power, and can drop engine temperature by more than 20 degrees F. The water pump run time can be adjusted from the dash control unit, allowing water flow to be tailored to your cooling requirements. An in-bed, 10-gallon water tank provides sufficient water reserve for extended trips, or water can be drawn from the trailer's freshwater tank through a hitch-mounted hose and fitting. Bidena Products, P. O. Box 7675, Dept. TL, Laguna Niguel, California 92607; (949) 661-9319; www.bidena.com.
March 2001
Bidena's Desert SuperCooler offers a simple, yet effective approach to keeping your engine cool, even under the harshest towing conditions. A dash-mounted control unit periodically turns on the special Shurflo water pump, which dispenses a pre-measured amount of water through spray nozzles to the front of the engine's radiator. The company says this cooling spray increases the radiator's cooling power, and can drop engine temperature by more than 20 degrees F. The water pump run time can be adjusted from the dash control unit, allowing water flow to be tailored to your cooling requirements. An in-bed, 10-gallon water tank provides sufficient water reserve for extended trips, or water can be drawn from the trailer's freshwater tank through a hitch-mounted hose and fitting. Bidena Products, P. O. Box 7675, Dept. TL, Laguna Niguel, California 92607; (949) 661-9319; www.bidena.com.