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Real easy to permanently eliminate this risk of trapped air. I added dynamic air vent to my cooling sys. Then drained coolant and refilled to verify how effective it is. No longer needed to purge sys, it does it automatically any time air is in system.
Air always rises to the local high spot. Just drill and tap 1/8" npt nipple that location. Then run tube to higher point in system. So I ran one from my highest point on engine block to my swirl pot. My radiator design also allowed trapped air, so I teed that into the vent too.
I'm now installing second engine. Now that I realize how important a dynamic vent is, I was able to design and place components so there is only 1 high spot...the swirl pot. Impossible for air to get trapped.
Easy to overlook value of dynamic air vent because there are so many other things to watch for.
-al wick
----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>
Chris,
For my installation, I need to burp the engine 3 times to ensure getting all
the air out of the cooling system. Failure to do so can lead to overheating
without you necessarily being aware of it. Here's what could happen. If
you have air trapped in the system, you can pour in coolant an it will
appear full. But, air trapped in either the block or the radiators can
prevent your engine from getting a full coolant charge.
To make matters worst, the lack of coolant in the system could (if low
enough) deceive your temperature sensor. The sensor will report a lower
temperature than is correct if they are not covered by the coolant as air
does not transfer heat to the sensing element as well as water. So your
temp gauge (even if calibrated) could be reporting a lower temperature even
as you engine cooks. One thing that always happens when my rotary has
gotten hot (even if it survives it) is the engine pings like crazy after I
shut off the engine during the cool down process.
Tracy Crook pointed out to me on a visit one of the first things to do when
checking for cooling problems (may not work depending on your cooler
orientation - mine are vertical) . When you are ready fire, up your engine
and let it run for no longer than a couple of minutes. Shut the engine down
and feel with your hand along the tank of your radiator. IF there is air
trapped in it you will notice it by the fact that the part of the radiator
tank with air will not be as warm/hot as the part filled with coolant.
Using this I discovered that after a complete fill of coolant my radiator
would be filled about a third of their volume with air!. After each engine
run, I could tell the air was leaving as the hot part of the tank increased.
I leave my radiator cap off/loose when I do my burping run-ups so the air
can readily escape. I then normally have to top off the header tank with a
pint or so of coolant for about 2-3 times.
Now I will admit that my system is not as well designed as it could be about
getting trapped air out, but, Lynn has said the problem exists even in auto
installations.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://www.andersonee.com
http://www.dmack.net/mazda/index.html
http://www.flyrotary.com/
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
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