Hi,
I have a 87 4/4 and had exactly the same problem with my car and in many ways i still do..
Try a fan override switch but like you it does not bring the heat down much.
Also have new radiator in the car with a thicker core for extra colling.. is better as car runs at 80 to 90 normal so more to move to heat up.
Also tried a new temp sensor, which can also help if it is faulty..
So all in all I have tried everything but the water pump.. in the end i feel it is a general problem with the car.
I would be delighted to find a solution to prove me wrong.
Will
