l have renault espace 2L RN Helios,it is a 94 model, the problem is l have just been away and it kept over heating. l noticed that in traffic the fans cut in and cool it back down, but while driving at 70 it gets hotter and hotter and then boils all the water away. l have checked for leaks and cant find any and the head gasket has not blown (YET). if you drive at a steady 60 l dont have a problem. as l said the fans cut in while stuck in traffic but they arent designed to come on while driving because of all the cold air rushing through the radiator. the water pump is working as you can clearly see the water being pumped round when you take the expantion tank lid off. i'm thinking a sticking thermostat but am looking for all possibilities before l start to fiddle with it.

With no leaks, water pumping, and fan working correctly. l will assume a sticking thermostat also. Also when is the last time you flushed the radiator? Build up over the years can cause overheating similar to this.

l had a similar experience with my Nissan Serena, and it turned out to be rust blocking the heater matrix, coming from the radiator. The system was back flushed, and refilled, also putting a sealant in, and so far, has run a dream.. worth a flush l think..