hmmm. not an easy one.

So, yes, I have no problem imaging you have a defective temperature sensor. It happens.

I would check the grounding first - do you have good ground between the block and frame (the ground strap is in front of the right front wheel, attaches to (or near) the motor mount. Second is the mounting of the sensor itself - any chance you used rtv / antisieze / teflon tape that might be interfering with the ground connection?

The good news is that the sensor can be replaced without dismantling the water pump and thermostat assembly...

__________________
David.X5
2001 X5 4.4i Sport
SOLD! at 160k miles