Welcome to JA.
First make sure there is no air in the system it can cause the temp guage to fluctuate remove the plug on the top of the radiator and pour coolant in it and in the resvoir until both are full. Then you need to have a pressure test done to check for leaks in the coolant system. But from what you are saying it sounds like a clogged radiator. So what you need to do to check for this is to get an infared thermometer and bring the car up to operating temp. Check the temp on the radiator from top to bottom. It should be hotter on the bottom and progressively cooler towards the top radiator hose. If you find any spots that are excessively hot compared to the rest of it that is your clogg. Given the age this is most likely the problem. This is where I would start. Thanks Daniel
Ok good. The whole cooling system needs to be pressure tested with radiator in the vehilce if this was not done. This way you know that there are no other leaks. Make sure there are no blockages in front of the radiator. leaves etc. and that the belt driven fan is working properly. The electric fan comes on with the ac so that pulls more air and cools it better. If you cut the car off after it has been running and hot turn the fan it should have drag and only turn about 1 time. Also if the fan shroud is broken or missing the top piece over the fan it will not channel the air right and will cause it to heat up. Let me know. Thanks
The belt driven fan has the fan clutch and it seems to not throw that much air. The shroud is in great condition and channels the air fine.
How much play or how hard or soft should the fan clutch be? If the fan clutch was bad would it be doing what it is doing(temperature fluctuate)?
How can I ensure to fully remove the air from the colant system?
Daniel how do I know I have the air out of the coolant system? What do I look for?
When you say fill the resovoir coolant tank is that to the fill level or top it off?
Sorry I didnt answer that part. There is a 21mm plug on the top passenger side of the radiator. Take it out and fill up the radiator until it is to the top. This will partially fill the resvoir up. Then fill the resvoir up about 3/4 and you should be good. When you put the plug back in dont tighten it too tight or it will break.
I will try checking the air in the system and have the system pressure tested. Can the radiator guy check with pressure for the leaks in the coolant system?
How do I do it to ask for you tomorrow if this still doesn't work? What other cause is possible if this does not work? Believe me I want this to be the issue!!!!
Land Rover has only one electric fan working!!! Would that be the problem???