In article <"004A63B0403E2084*/c=us/admd= /prmd=Cat/o=NOTES/s=Gosling/g=
Richard/i=B/"@MHS>, Richard B Gosling <Gosling_Richard_B@perkins.com>
writes
>Mike wrote:
>
>"I may do this, come the autumn. I find the idea of having a winter
>thermostat and a summer thermostat appealing!"
>
>I have heard of other people changing their thermostats with the season, and I
> don't really get the logic of it.
Let me at once admit that I have little or no knowledge of what is
supposed to happen under the bonnet of my car. I am a technical and
mechanical illiterate.
> An engine is designed to run optimally at a
> specific temperature - no hotter, no colder - and this temperature does not
> change with the weather. The thermostat is intended to maintain this optimum
> temperature, by preventing water flow through the radiator below the fixed
> temperature, and allowing full flow above it.
>
>Having a "summer 'stat" will NOT do anything to prevent a car overheating in
> the summer. Once the engine reaches the critical temperature the 'stat clicks
> full open - if the proper 'stat is an 88 deg C stat, at 89 deg it will be just
> as open as a 74 deg stat. All a low temperature 'stat will do is make it
> difficult for an engine to reach the optimum running temperature, by giving
> the engine full cooling as soon as the coolant temperature reaches 74 deg.
Having given some thought to this, I am forced to the conclusion that
having a "summer stat" is only going to be of benefit to cars where
overheating on short journeys can be a problem. Such as, for example,
old cars with impaired coolant flow through the system, due to corroded
pipes and heavy limescale deposits in the radiator.
Given that overheating can be a problem with old cars, the fact that my
thermostat appears to be permanently open should mean that the time
taken for the engine to get hot is longer than otherwise. Applying
this theory to a short drive on a summer's day means that despite high
ambient temperatures and traffic jams, Carly won't overheat, although
she will take longer to reach optimum operating temperature. In the
winter, on the other hand, I want the engine to warm up as quickly as
possible, and therefore I would want a thermostat which stayed closed
until the correct temperature was achieved.
I should mention here that I am paranoid about overheating engines.
This is as a result of running a Sunbeam Stiletto some years ago. The
Stiletto has a Coventry Climax engine, which is a great little power
plant, and gives 7-second 0-60 times. It was designed, however, as a
motor for fire engine water-pumps, to be cooled by the thousands of
gallons of cold water that were being pumped. The poxy little radiator
that Rootes Group fitted to Stilettos was really not up to the job of
cooling, even when new. After twenty years of use, the flow within the
cooling system was probably at around half its design volume, and long
journeys in the summer had to include frequent stops in the shade to
allow the engine to cool down. This was in a car with a comparatively
large oil cooler. Carly doesn't even have a small oil cooler.
On a related note, Carly and I are setting off on a 250-mile journey in
a few hours' time (Bedford to Richmond, N. Yorkshire, via John and
Saskia and the Spitfire Graveyard in Sheffield). Wish us luck,
everyone! We hope to be back in contact on Sunday night...
ATB
--
Mike
Michael Hargreave Mawson, author of "Eyewitness in the Crimea"
http://www.greenhillbooks.com/booksheets/eyewitness_in_the_crimea.html
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