> The heated and expanded wax causes the thermostat to open against spring
> pressure. As the wax cools, the valve is closed by the spring pressure,
> not
> "suction" of contracting wax, which would probably cavitate anyway.
> As such, when the wax is lost there is nothing to push the valve open and
> the spring returns it to the closed position, so failing in that position.
>
> I agree that the older mechanical versions fail closed.
>
> The Mocal version of oil thermostat bypasses the cooler when "closed".
>
Forgive me Duncan, but if I follow your logic then the Mocal thermostat
would fail in the cooler bypass position - that is opposite to the ideal
failsafe position.
regards,
Mike
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