> 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,
Paul went off to play in Florida for a while, so I am sending this direct.
When you say a pressurized overflow bottle, do you have it plumbed so that a
pressure relief cap on the main system feeds the overflow into the
pressurized plastic bottle, and then the 10 psi pressure in the bottle pushes
coolant back into the system as you desend under low power (where the engine
would cool off some) and keeps the overall system pressure at 10 psi?

It seems that this must be the way you are doing it, because otherwise I
don't see how you could get 17 psi with a 10 psi cap.

Thanks for any information. I am plumbing my engine now.

Bill Schertz
KIS Cruiser #4045

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