On Fri, 13 Jun 1997, Michael Fisher wrote:
> Ray,
>
> I think I see the problem here. The thermostat does not really restrict the
> flow in the sense you are talking about. With a thermostat you essentially
> have two closed loop systems, one in the engine being heated and one in the
> radiator being cooled. The thrmostat acts as a switch to change the working
> fluid between the two closed systems, in total, then it closes again to
> separate into two closed systems. That is why the engine runs cooler with the
> thermostat.
I was with you, right up to the last line. Yes, under ideal conditions,
the thermostat cycles between open and shut, but the purpose is to keep
the engine temperature *higher* than it would be if there were no
thermostat. If you have a 180 degree thermostat, it opens at 180,
permitting coolant flow until temp falls below 180, then it closes,
forcing the engine to run at 180. If you have a 190 thermostat, if
forces the engine to run at 190. If you remove the thermostat,
coolant flow is continuous. The engine will run at a temperature
determined by air flow, power production, etc. If the engine was
running at 180 with a 180 thermostat, it will generally run at some
temperature *less than* 180 without the thermostat.
Most of the arguments on other lists have had to do with the situation
where the engine is overheating, i.e. running hotter than the thermostat
setting. In that circumstance, the thermostat should always be open,
providing only a slight restriction to flow. It has been argued in that
case that removing the thermostat will make the engine run even
*hotter*. I doubt that, except in the case where the slight restriction
posed by the open thermostat prevents water pump cavitation, or if the
restriction somehow results in more even flow, or in a few cars where the
open thermostat actually does redirect flow by design.
WRG
W. R. Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons(at)northpole.med.uvm.edu (802) 656-8629
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