Hi,
No offense, but, it will give you an accurate temperature. What you
are looking for in that case is the relationship between what your
dash mounted gauge reads and what the thermometer reads. So, if your
gauge says somewhere between C and H and your thermometer agrees, then
you can trust your dash gauge.
When you put the cap on and the pressure rises, you can still trust
your dash gauge to be in the ballpark.
Measuring the temp in that way will not give you an accurate temp for
normal running conditions, but that isn't what he was looking to
measure.
BTW, the spridget cooling system is closed and does build up some
pressure when the temps rise. Otherwise, you would loose coolant to
operating conditions and evaporation.
Cheers,
Derf
On 5/25/07, Jim Johnson <bmwwxman@gmail.com> wrote:
> Bud wrote:
>
> Years ago, I stuck a
> > thermometer in the radiator tank, with the engine starting from cold,
> > idle, and just noted what the thermometer read, compared to the gauge,
> > as the engine warmed up. Pretty easy to do, and it won't puke much
> > coolant out of the open filler plug hole, while idling.
>
> Bud.... This also won't give you an accurate temperature! Recall:
>
> PV = nRT
>
> Temperature (T) is inversely proportional to P (pressure) and V
> (volume). If you leave the radiator cap off, the system is not
> pressurized thus Temperature will be different than if the system is
> pressurized as it normally would be.
>
> Big question which I alluded to the other day when Frank had his
> problem - "Is a spridget cooling system pressurized??" If it isn't,
> you are okay, but I'm thinking it has to have at least some pressure
> in it due to expansion from heat and the fact that the system is
> closed.
>
> Cheers!!
> Jim - 68 Midget in Dodge City
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