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Water temperature gauge and ether?


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I'm having my smiths gauges reconditioned and I've just found out that the metal cable attached to the back of the water gauge is filled with ether.  I've read that it is very flammable but can some one explain in simple terms what it is used for and why?



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Ether is very flammable, explosive even, but there is a very small quantity in the guage and the "bulb" at the sensor end, too little to cause concern even if it leaks.    AS the system is filled with the liquid, there is no risk of fire inside it.  No oxygen!

The operation of this type of gauge is that the liquid in the bulb is heated by the coolant and expands.    The bulb is closed except for the tube that connects it to the gauge, so the liquid is forced up into a 'bellows' whose expansion moves the needle.  Probably a 'Bourdon tube', not a bellows but the word conveys the idea better.

The bulb and tube are filled with the liquid, which may be ether or an alcohol, both with a freezing point ten times lower than anything a car will meet.       Water would be unsuitable because of  the anomalous expansion of freezing water, that would rupture the bulb or pipe.


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