Why is my 1994 Nissan Quest dash temp gauge pegged to hot but engine does not appear to be overheating?

Check your Coolant levels. In most cases this indicates air in the Coolant system. Often you will get no heat from the heater to go with this problem. There is a bleeder located on top of the intake manifold which is the highest point in the cooling system which allows the system to be be bled of air.

Another way is to raise the front wheels or park the van up hill both which raise the rad height. Remove the cap when cold and run the engine until all the bubbles stop. Keep topping up the fluid.