I got the "new" engine in and running. It is from a wreck with 77,000m. I find that it will idle for an hour with no overheating issues but once I start driving it, the temp starts to climb 15 minutes into the run. When this happens, I cannot hear the fan, in fact I only hear that whine when I first start it cold. I had to pull over yesterday to stop it from boiling. I waited 10 minutes and on startup, the fan did not engage. Can anyone tell me which sensor turns this on and off? I don't want to start changeing parts unless I know where I should be going. My scrap motor is in the shop so I have an extra water pump, thermostat ECM and what ever I may need. With the motor idling and the temp at 212 (from my scan tool), the fan is not engaged. I unplugged the connector and no change, but this did give me a code that the fan had lost signal. Thanks!