cav551:
Have we established whether this is a FORD Cargo or an IVECO cargo? I seem to recall changing plenty of rotten or furred up Ford rads back when they were an everyday fleet motor. If it is a Ford does it still have a fan cowling? it’ll run hot without one. Also think the Ford had a viscous fan, which needs to work, but it was a long time ago.
Tbh; I’ve never had any Dover engined ‘proper Cargo’s’ that have done this. It is though an issue I have come across with older model 75E 15’s (Iveco Cargo’s) say around M-T reg. The rad’s aren’t big enough imo for hot weather and they ‘cake up’ fairly easily too. I remember my time in television facilities towing a toilet, with the main truck being a short wheel base box van (ex-fridge) with a generator on board. Any sign of a fair sized gradient and the temp gauge would go 3/4 the way over in hot weather (80ish degrees F). Putting the heater on full, with the blower on max stopped it from going into the red. I remember we did flush the rad with bicarbonate of soda and that helped (though it would still run hot in high temps).