Does your heat work?
Sometimes the cooling system needs to be bled properly in order to remove any air trapped in the system, the air can cause false or varying readings if it's in the right place.

Otherwise, if your engine is hot to the touch and there's no reading on the temp. gauge (which should show temp. even if the water pump fails), it could just be the temp. gauge sending unit or something with it's electrical connection. It's the smaller of the two in front of the distributor (slightly in front of it).
The resistance of the unit should be 142ohms at 133degrees F (56 C) or "cold" and 49-32ohms at 185-212degrees F (85-100C).