Walt. Thanks, I hadn't considered the impeller. The car done <12,000 miles, with fewer than 400miles in the last 12 years! I purchased it two months, and ~80miles ago. The thermostat is brand new and all the easily visible hoses appear OK. The first trip I took was ~20miles birnging it home on an empty motorway. I have been careful not to exceed ~60mph to run the engine in again, but even in this trip with constant airflow due to the motion the gauge got very high. The test dirves before purchase were relatively short, and the previous owner didn't take it on long trips so the problem may have been hiding for some time. I have wired a bypass switch so that I can run the cooling fans constantly but this does not improve the situation whilst in motion. John Chapelhow Another thing to consider, however rare, is that the water pump impeller could have come loose and is spinning on the shaft. Also check that the coolant hoses/pipes aren't crushed or kinked. Did the car aquire this problem suddenly? A radiator isn't going to clog overnight. Walt Tampa, Florida