My 30 year old 110 with a defender 200tdi in, when driving or towing a light trailer I get a tiny bit of movement of the temp gauge but otherwise all normal but when I tow a heavy load a fair way the area around the seat boxes and gear stick get as hot as I would love the heater to get on full chat, too warm to leave your leg there, is this normal? It has just had a full service so all fluid levels correct. This was in hot weather last Fri and the engine gauge had crept to the top quarter. Only tow the heavy horsebox full of scout stuff once a year but have noticed it with the loaded caravan on hills too. Is it just the wash of hot air channeled from the engine bay?