I guess you're joking, but some ground and in the air (near airport) testing should be fairly easy.
Drain enough coolant so that the level is just below where you want your warning to start. Run the engine at various power levels and attitudes and notice the behavior of the indicator. Add a bit of coolant and repeat. After a bit of such testing you should have a pretty good certainty that your indicator works the way you want it to. In normal orientation (not plugs up), you should safely be able to run the engine with a pint and maybe even a quart of coolant missing. At a guess the danger level is when only 1/2 of the pump impeller is covered with water. You warning level should be significantly higher than that. Of  course if you do the testing while you have a real leak that's a different matter :)

Finn

Jim Sower wrote:

<... Obviously is going to take some testing and trial and error ...>
How would one test a fluid coolant indicator?  Fly around for a while and then dump some coolant over the side and see if the warning light goes on?  Create a small leak to see if the pressure gauge actually does indicate a problem before temperature rises or fluid gets too low?  The trial part could get pretty dicey.  Now, what about the error part?  Who's gonna' be your test pilot?

Can I watch? :o) .... Jim S.
 
 

Finn Lassen wrote:

Jim Sower wrote:

> <... Why wouldn't the pressure increase when water levels drop and
> steam develops? ...>
> Need to work backwards on this one.  If the water level drops, one
> would deduce that it happens for a reason, and a leak comes
> immediately to mind.  When the cooling system starts leaking, the
> pressure drops off substantially quite a while before any significant
> drop water level.

I don't agree. A minor leak (pin hole) will not cause a significant
pressure drop. Sure, loosing the cap or a hose the pressure will drop.

>   FIRST the pressure drops precipitously, and THEN the coolant level
> starts to go down ... FINALLY the temps start to rise (provided the
> temp sender is submerged in what water remains).
>
> If you were to use a coolant level indicator, where would you put it?
>
Yes, that is a tough one. Somewher in the upper part of the pump
housing. The whole idea is to get an early warning - must be able to
loose more coolant before pump stops pumping, so you can make it to the
nearest airport without frying the engine.

>   Not in the block, because Ed has established that what coolant
> remains is relatively well distributed in the block.  In the expansion
> tank?  I would suspect you'd get a lot of "false negatives".  I don't
> know where I'd put one, or how much to trust it.
>
> Just a theory .... Jim S.
>
Obviously is going to take some testing and trial and error.

Finn

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--
Jim Sower ... Destiny's Plaything
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T