Dick, I have no idea how or why, but I have heard of this before. If there is no coolant passing the sensor it doesn't set off the idiot light. This seems like what happened to me, since after I filled it up it eventually came on.' Rob Tip to those who don't already know: Don't overheat your car twice in one day, don't drive it with no coolant and after you overheat it, change the oil and don't try to drive home on the highway. Also avoid the Long Island Railroad @ 4 am on a Sunday and don't try to push your car wearing flip flops > >Take a look at one of these sensors, then tell me what keeps the >temperature >of the casting into which it is threaded from being sensed at the core of >the sensor, which is inside a brass cylinder, which in turn is in contact >with the threaded outer case. I think it has to read the temperature of the >water jacket - there isn't anything cooler in the vicinity to confuse it. >If the water jacket is cooler than the coolant, it's a mystery to me as to >how this can be. Hotter I can understand, but not cooler. > >Dick Benjamin _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx