It slowly gets hot

 

Holy ****.. I put the old gauge sensor back on and it’s running great.. tht thing caused so much trouble.. thanks yal fr

 

The sensor grounds through the block. It may have had a bad ground. Get yourself an infrared thermometer just in case. They are fairly cheap at Harbor Freight for a basic one. Once you have one, you'll find other uses for it.

Checking the thermostat operation, looking for a misfire by finding a section of exhaust manifold that isn't hot enough, checking steaks on the grill to see if they're done and so on.