its ok to remove the thermostat but your car will take forever on cold mornings to warm up. also the hose coming from the bottom of the radiator likes to cinch itself closed when there is no thermostat causing overheating. Its best to just get a new one or clean out the one you have. the fan is activated by the coolant temp sensor next to the thermostat housing and intke plenum. it is a small plug that with wires that can easily be cleaned or plugged in firmly to be fixed instead of getting a new one.