Car is running hot (temp gauge rises above normal)

the usual suspects are:
stuck shut thermostat
clogged raiator
dead water pump
low coolant level
it's sunday, rovers don't work on sunday.
Then again, maybe its wednesday, rovers take half a day then.

One way to tell a bad thermostat in a car is if the car overheats frequently even if there is water in the radiator.Stuck open - no heat from heater, temp gauge hardly moves off of cold.
Stuck closed - overheats engine, temp gauge quickly climbs to hot.listen for any rubbing, grinding, or whining noises from the pump. look under water pump while running, if pump is going bad. water will come out of weep hole on the bottom of the pump. good-day!

Loosen of the tension on the belt. see if there is any movement in the pulley (up-down -in -out Spin the pulley and check for roughness in the bearing.; Check for water leaking from the small hole in the housing at the base of the pump housing . Refit belt and correctly tension if nothing found. Check when it over heats (idle at lights) hard runs (speed) starts when cold and temp gauge continues to rise after engine is hot check if fan comes on at all.. Is the engine actually getting hot or is it an indication from the temp gauge ( faulty temp sender). If all is ok engines run hot if they are running lean so check the o2 sensor in the exhaust

check that temp thermostat is activating when temp rises above normal

Sounds like a faulty temp guage/r a strange malfuntion in a sensor to me as well, only doing it when it going up hill really makes no sense for the way the cooling system works so I doubt that its actually running hot, which is likely why he asked about the gurgling noise, it would force water back into the resivoir if it was running hot assuming that the thermostatic radiator cap is working properly.

It could be the impellor wearing out on the water pump, though I have not heard of this issue in your make of car, I have seen it first hand in other makes. The thermostat may not be opening up all the way, flow restriction,. The coolant temperture sensor could be going out, and the gauge in the dash could be going out. You could have flow restrictions else where in the engine. Have you ever had the engine flushed? these are the things that I can think of that would make your engine run hotter than normal.

either thermostat or water pump impeller drive shaft

On a vehicle this age, it is likely that the fans themselves have worn out. Test the fans by running battery power directly to the positive contact. If they start, they are OK. On 4.3 motors, there is also a seperate temp sensor to signal the fans, usually called a fan switch. I believe it operates independent of the ECM. Another possible culprit is a bad ground at the fans or even a loose or corroded negative battery cable.

they are designed not to fluctuate with engine temp and are kept stable once operating temp is reached. only if the temp exceeds a set mark will the needle rise to indicate overheating,

Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.