Classic/Antique Car Repair: 1926 rolls radiator, wind tunnel tests, grease monkey

Question
My 1926 20 HP Rolls is overheating. The repair man said he cleaned out the
radiator but the temperature gauge goes to 100 as soon as you stop driving.
As soon as you drive the gauge goes down immediately but I am afraid the
high temperature will damage the motor. He said I should have the water
pump rebuilt (for about $1000) but I see the water being pumped when I take
the radiator cap off, so it looks to me like the water pump is working. How
can I get the temperature to go to 100 as soon as I stop at a traffic light.

Answer
Hello David. first of all I hope you have performed your due diligence on the person servicing your Rolls. A little knowledge is a dangerous thing when it comes to antique Rolls and Bentleys. You are correct the water pump is fine, leave it alone and apologize to the grease monkey for me. since I have prevented him from scalping you for a grand needlessly. Well now that the unpleasantness is over lets visit your grand lady, in the era she was created there was little knowledge regarding airflows (no wind tunnel tests) so the fan shrouds that you see on cars from the seventies on up did not exist back in the 20s. Cars then did have a rise in temp at idle the fan simply could not pull sufficient air through the radiator due to low idle speed, no shrouds, and small fans. the challenge here is to determine that first the car is functioning the way it was designed. and then if, BIG IF. you may help it with modern technology. so first off is the engine block's coolant passages free of debris and corrosion, are the engine settings ignition, carburettor, valve clearance, done to Rolls Royce specs and NOT ACCORDING TO SOME MECHANICS EAR. if yes then you may consider an electric fan wired to run through a temp sensor NOT DIRECT and mount it so that nothing original is damaged. I hope this helps you David. are you in Florida by chance? Best Regards George