View Single Post
  #24   Report Post  
Old June 10th 06, 02:00 PM posted to uk.sci.weather
Alan White Alan White is offline
external usenet poster
 
First recorded activity by Weather-Banter: Jul 2003
Posts: 3,740
Default Accuracy of car thermometers

On Sat, 10 Jun 2006 09:14:58 +0100, "Will Hand"
wrote:

Yes fair enough the radiator will warm quickly and dry. I was only suggesting
how the mechanic could have been right.


....but the radiator doesn't warm up quickly. The radiator only warms
up after the cylinder head thermostat opens and diverts hot water in
the cylinder block through the radiator. Under freezing conditions,
this can be some minutes after the engine fires up.

Try this. The next time you drive in cold weather keep a close eye on
the temperature gauge. The temperature will rise to almost normal,
then drop back and then continue its rise. The point at which it drops
back is when the head thermostat opens allowing cold water from the
radiator to circulate around the block and, in so doing, temporarily
reduces the water temperature in the block. The water temperature then
continues its rise until a state of equilibrium is reached, that state
being determined by the setting of the head thermostat.

Having said all that, the thermal mass of the water filled radiator
mitigates against any significant cooling effect generated by the
evaporation of an external film of water.

--
Alan White
Twenty-eight miles NW of Glasgow, overlooking Lochs Long and Goil in Argyll, Scotland.
Web cam and weather:- http://www.windycroft.gt-britain.co....her/kabcam.htm