Hi I noticed funny thing on my car(its 98 1.8 SE) while driving at about 50-70 mph engine temp gauge drops to about 70 but when i stop in few mins it goes back to 90 and will drop again if start driving for a few miles at same speed. Thermostat was changed a while ago cause wasnt closing. what else could it be? Faulty thermostat temp sensor or viscous fan? Thanx for any help.