He and anyone else can run the car with the rad cap on only one click. That way the fluid will not be pressurized and not blow out the overflow but will still circulate and take some heat from the engine to the rad. I'd check to see if he's got air in the system. An air embelism? will make the car overheat quickly. to remove the air, drive the car as above for 35+ minutes to let the water circulate and the air move to the the top of the rad and out of the 1/2 open cap. He should also make sure the heater core is open, heat settings on hot. No need to run the fan motor unless the driver is cold or car starts to overheat during the air bleed. If the car runs hot after that, remove the rad and have it boiled out. or recored.