[michaeljp86]

Its a 1992 gmc jimmy 4x4 with auto trans. I had a bad head gasket and just finished getting the engine back together. I fired it up and had the radiator cap off wanting it to warm up and get all the air out of the engine so I could top of the radiator. I had it running for about 20 min and the temp gauge never showed anything. I took it for a little drive and still showed nothing.

There is 2 temp sensors on it, one in the intake manifold next to the thermostat and another on the passenger side cylinder head.

I played with the connection on the sensor on the intake and the gauge showed nothing. I played with the sensor on the cyl head and I had it 1/2 way pulled off the the gauge showed just above 0. I plugged it back in and it stayed showing a little above 0. As soon as I hit the brake and put it in reverse the gauge went back to 0.

It probably ran for over 30min and the sensor on the top of the engine felt hot when I was playing with the sensor so I know the engine was warm.

Anyone have any idea on whats wrong? The sensor on the cylinder head was replaced not to long ago and the gauge always worked fine.