Ed Anderson wrote:

It is my opinion that a coolant pressure gauge is a better early indications
of a leak rather than coolant temperature.  By the time your coolant temps
start to climb (even if the temp gauge is reporting the condition accuracy)
you are already in sufficient trouble that probably only turning the engine
off and becoming a glider is going to save the engine from damage. The
pressure gauge may provide an earlier indication as the system fails to
pressurize (after engine start) or pressure starts to fall from levels
normally seen for that stage of flight.

Why wouldn't the pressure increase when water levels drop and steam develops?

I still think the best leak detector would be a water level sensor. Petty that the solid state one for fuel tanks is not designed to handle higher temps:
http://www.ppavionics.com/LFL.htm

Here's a mechanical that Rusty found earlier:

http://www.grainger.com/Grainger/productdetail.jsp?xi=xi&ItemId=1611587508


Finn

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