Suzuki: 1996 vitara overheating, fan clutch, driven fan

Question
QUESTION: Hi our 1996 vitara is over heating on motorway runs it gets up to the red zone. Its does not over heat around town. I have checked the fan and it is coming on when the motor is hot.

ANSWER: I suspect that possibly the thermostat is not opening far enough to permit sufficient flow of coolant under the higher engine loads(and more generated heat) of higher speed driving.
Another possibility is that there is debris blocking the radiator and sufficient air is not flowing through the radiator to exchange the additional heat of higher engine speeds and loads.
One other thing that I occasionally see is that the cooling system had straight undiluted antifreeze in it.  Anti freeze carries much less heat than a water anti freeze mixture.

---------- FOLLOW-UP ----------

QUESTION: i have flushed out the system and when doing so found that the fan surround was not secure at the base and had been rubbing on the belts etc. it is now secure would this had a effect at all? I have not been on a motorway run yet to check it out.

Thanks Again

Graeme

Answer
It's possible that the surround was not pulling enough air through the radiator.
It's possible the belts are slipping.
It's also possible that the viscous fan clutch for the engine driven fan to have a problem and not be pulling enough air through the radiator.