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Bob, if there is no air in your coolant system, you may be
observing an hydraulic lock type phenomena. My water pressure will
immediately zoom to 21 psi on engine start up. As the engine warms up the
pressure drops back down. My understanding is that with no air and the
incompressible nature of a liquid - that even small perturbations anywhere in
the system can cause the sensor to signal pressure. As the engine warms
and a very small amount of expansion in block, rad cores, lines etc. happens
that is enough increase in volume of the "containment" for the
pressure to lower.
This is why some folks recommend leaving a small amount of air
under the cap. If you are not seeing oil in your coolant or bubbles then
its unlikely you have a busted O ring.
Ed
----- Original Message -----
Sent: Sunday, February 24, 2008 11:52
PM
Subject: [FlyRotary] Water pressure
I ran my 20B at idle, till about 160 degrees. My water pressure rose up
to 23 lbs. That seems excessive to me, but I've never watched water pressure
before. I've bled the block a couple of times and I dont feel like I have an
air lock. Heat is even throughout the radiator. I was a bit worried about
compression leaking into the cooling chamber, but I'm not loosing any water,
the plugs aren't wet, and it starts flawlessly each time. Hot or cold. Recon
I'm all worried about nothing?
Bob Mears
Supermarine Spitfire
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