Running hot or is it?

I would go ahead and change out the engine temp sensor and temp sending sensor- both are located above the thermostat area. They are cylindrical copper sensors that screw into the housing. They aren't very expensive and if they haven't been replaced yet, might be a good time to do it. I'm not guaranteeing this is the fix, but it's a good start and won't cost much. Also, replacing the t-stat would be a good idea. The t-stat is not very easy to reinstall as it's in a tight location, but if you're mechanically inclined, you'll figure it out! Make sure to use a Nissan-brand stat also.

Chris

All good suggestions, but this may also be a sign that the water pump is failing. A worn out t-stat is more likely to show up as an engine that won't get warm, not one that is running hot. He could also have worn blades on the water pump and not getting good coolant flow.

When is the last time the water pump was replaced? If it's been over 75k miles, then you should think about doing the entire water pump/timing belt replacement. And do the t-stat and sensors while you're in there.

Bill G '91 SE Auto

Not if it's not opening at the right temp or not opening up all the way..

That's not very likely, I've seen probably 3 in 25 years of working on cars and all 3 had straight water in them for years.

My guess is the radiator is crapping out. He needs to find out for sure if it's actually running hot or not and fix it if it is before it ruins the engine.

How does the inside of the radiator look, could have build up in the vanes restricting water flow. Is this original radiator? When was coolant changed out? If radiator looks good and fluid change is recent. I would change