writes: After you shut off your engine, the 7 psi gradually drops over the next few minutes. It only takes around 12 minutes for the system to develop a vacuum relative to atmosphere. At that point the little valve in the radiator cap opens and allows fluid or air to flow into system. (Check out your rad cap, can you find both valves?) --------------------------------------------- Al, if your cap is a 24 psi cap which you said you could run with full bottle. Why does it develop a vacum on cool down. I have never noticed this on my system, but on the other hand probably never looked at it 12 minutes after shutdown ----__JNP_000_4676.34b5.3996 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: quoted-printable

Was said: <Why does it develop a vacuum on cool down?>

Let's explore this. Let's convert this theory to facts.

Just use your favorite drink container. No, not a beer can.

1) You can use any container that has a small neck. Fill container = with=20 water, place a balloon over the bottle neck.

2) Put a pan of water on the stove, turn to high heat, place your = drink=20 container inside.

3) As it heats up, you will see the balloon expand. When it cools down= , you=20 should see balloon suck into bottle.

Heated coolant has excited molecules that get further apart from each= =20 other. As it cools, these molecules get closer together. It's a tremendous= =20 force.

I did all sorts of little experiments like that with my plane. Like I= =20 covered one exhaust pipe with rubber and watched how it behaved. I = installed an=20 atmospheric pressure sensor inside exhaust and watched the pressure pulses.= =20 There are a lot of physics principals that we don't have a good grip = on=20 because they are difficult to measure. I work in science museum where we = expose=20 people to these every day. It's a blast.

-al wick
Artificial intelligence in cockpit, Cozy IV powered by= =20 stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland,=20 Oregon
Prop construct, Subaru install, Risk assessment, Glass panel = design=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html

On Wed, 8 Jun 2005 22:31:57 -0400 WALTER B KERR <jbker@juno.com> writes:

On Wed, 8 Jun 2005 19:05:25 -0700 al p wick <alwick@juno.com> writes:

After you shut off your engine, the 7 psi gradually drops = over the=20 next few minutes. It only takes around 12 minutes for the system to = develop=20 a vacuum relative to atmosphere. At that point the little valve in the= =20 radiator cap opens and allows fluid or air to flow into system. (Check = out=20 your rad cap, can you find both valves?)

---------------------------------------------

Al, if your cap is a 24 psi cap which you said you could run with = full=20 bottle. Why does it develop a vacum on cool down. I have never noticed = this=20 on my system, but on the other hand probably never looked at it 12 = minutes=20 after shutdown

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