I need some help from some cooper experts! Should the motor fan come on when you turn the switch on? how long should it take for the fan to come on after I start the engine? R56 2007 MCS. I started the engine to flush the cooling system, " after doing a thermostat replacement" on my daughters MCS, and the cooling fan is not running, thank goodness she only drives about 10 miles or so at a time, school, work etc... now I am wondering if maybe the engine heat from fan problem possibly caused the thermostat problem!