LDV T60: Problems with engine temperature

I have recently posted a complaint about the brakes on my LDV T60. I now appear to have a problem with the engine temperature. On a recent trip with my van which weighs 2000 kg, on long hills the engine temp rose rapidly to just below the red zone and on two occasions the engine began to shut down, like running out of fuel. After a short rest the temp dropped. It did not boil or lose water from the tank. If this ute has a tow rating of 3000 kg what is going on.