Bob, how is your cooling system set up? I was getting high water
pressures and blowing out of the overflow when I had a pressure cap on the
radiator.
I changed that to a radiator cap that has no pressure containment valve
on the radiator, took the overflow hose from the radiator to the bottom of an
overflow bottle (a modified fire extinguisher) which has a 23# cap on it. The
overflow from this bottle vents to the outside, but so far, has never vented. The
bottle is about ¾ full of coolant. This eliminated my high pressures and
stopped all the blowing out of the overflow. I think that this is similar to
the way most of the cooling systems are set up on the list.
The air in the top of the overflow bottle prevents the hydraulic lock
that Ed is talking about below, but ensures that there is no air in the
circulating coolant. This didn’t solve all my cooling problems, but it
eliminated one of them. :>)
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of bmears9413@aol.com
Sent: Monday, February 25, 2008
10:11 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Water
pressure
Cool deal...thanks guys.
I have a 30lb. cap and havent let it get there yet to see if it blows out to
the overflow tank. I keep thinking that if I had a regular automotive 15lb. cap
it would already be pushing by that and its jsut idleing.
-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft
<flyrotary@lancaironline.net>
Sent: Mon, 25 Feb 2008 6:59 am
Subject: [FlyRotary] Re: Water pressure
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.
----- 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?
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