> Hi Paul
 > I changed my coolant recovery system to a small pressurised overflow tank
 > instead of the unpressurised original because the system had no

elasticity.

 > With short, very firm water pipes and small aluminium header tank the
 > pressure went quickly to cap pressure on start up and overflowed to the
 > recovery bottle. The overflow continued all the way to 10,000 ft. On the
way
 > down the pressure dropped to zero. This meant that I could not use my low
 > coolant pressure alarm, and also suffered some water loss.

 > With the pressurised system there is no water loss and the pressure
remains
 > above 10psi until long after shut down. Only a small plastic bottle half
 > full is required. The bottle is off a GM Camaro car.
 > The gauge reads about 11psi at 1,000feet. At 9,000feet it usually reads
 > 17psi. The cap, which is on the overflow bottle is labelled 10psi.
 >  I have a schreader valve to pump the system for cold testing, the cap
 > releases at 11psi. cold.
 >
 > Happy flying, Ian Rotary RV6A. Australia.

Ian
Do you have two pressure caps then? One on the primary coolant system, that
is set at a higher pressure, and one on the coolant bottle set at 10 psi?
Since your pressure at 9000 feet reads 17 psi? So as the water expands it
drives it to the pressure bottle, and the pressure bottle drives it back as
you desend at low power?

I don't understand the ability of a 10 psi cap to retain 17 psi otherwise.

Bill Schertz
KIS Cruiser #4045

 
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