Do you have a thermostat ? If no, the water will run thru the radiator too fast and not have enough time to cool off.
Does the thermostat open about 80º C, assuming you have one. You can check by removing it and putting it in a pan of water on the stove, and use a thermometer.
Are you running straight water? Should have some
antifreeze in there to up the boiling point, just in case.
I have an SPF with a mild 351W, and the water temp is always at 80º C in normal running. It has two small puller fans with temp control and they only go on at about 85ºC.
Just drove about one mile in a 4th of July parade (you know - the celebration us Yanks have after we beat the pants off you Brits
). Max speed was probably 10 MPH. Temp never went over 95º C.
There is another thread on the board regarding the Fan-Man. Just read it before seeing your post. Check it out.
Spal fan best place to buy?
Hope you and all your loved ones are OK and were not in London this morning.
Cheers from across the pond