Hi everyone! I just changed my water pump because it was leaking coolant all over the place. I started my truck and added coolant, but my temp. gauge goes right to hot when I start my car. The pin goes all the way to the far right on the temp gauge. Is my thermostat faulty? Do I have it in backwards?

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2001 X5 4.4i WHITE-Loaded like a baby's diaper SOLD