When I turn the key on the temp gauge automatically goes to the middle before the engine even goes on. Once the engine runs a few minutes it goes to red and then goes back to the middle once the thermostat opens (I am guessing). Just yesterday it never went back to the middle after running for a few minutes and then the temp warning light came on.

Today I removed the thermostat and ran it around the block a few times. The temp gauge never moved from the middle but the temp warning light came on again after about 15 minutes. The radiator hose running from the top of the radiator to the the engine was hot and full of pressure (is this normal?). I remove the overflow cap and the pressure released. Could the temp be fine and I have a faulty temp warning light? Any ideas?