over heating wen under load

hallo
i have a 90 300tdi thats started to over heat on motoway or at high speeds (55-70)mph wen tobying round town and in traffic it never over heats as soon as you get on a road or steeep incline the temp steadly clims has enbody got any idears
had a new water pump about 6 months ago
cheers rich

mine was the same untill i jetwshed the rad and flushed it, fine now, runs hot under load but not into the red.

Blocked rad core would be my starter.

When the Landy's been on a run - is the rad hot all over, or do you have cool patches?

Also is the top hose hot - if not could be a stuck thermostat

cheers lads have cleaned rad will test tomorrow