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Lynn,
Let me ask you a question that has puzzled me - perhaps you
have observed the same if you monitor your coolant pressure in racing (which you
may not). I (and Tracy) noticed a couple of years ago that immediately
upon start up the coolant pressure would go to 20-25 psi. Immediate fear
is of course a combustion chamber/coolant galley leak past the coolant "O"
rings. However, that turned out not to be the case. The
pressure would return to normal (5-7 psi) once the engine warmed up. This
did not occur right after changing the coolant but only after the engine had
been run several times. It would start showing up in my engine after about
the 3rd flight.
The best theory we could come up with is that all the air had
been removed from the coolant system and with an incompressible liquid
filling it completely - that the initial heat of combustion was immediately
causing the coolant to pressurize as even a smidgen of expansion would be
reflected in pressure (as there was no air to compress). Once the
engine heats up the metal expands and the volume of the coolant galleys increase
infinitesimally - but enough to lower the pressure. Once the engine heated
up the pressure would react normally - although at cruise the pressure would
often read zero.
In fact, Tracy has designed his new RV-8 3 rotor coolant
system to always maintain a small amount of air in the header tank so as to have
a more "normal" pressure gradient.
Have you had any similar experience or theory about a possible
cause???
Ed
----- Original Message -----
Sent: Monday, October 30, 2006 9:25
AM
Subject: [FlyRotary] Re: Copperstate
Fly-in (was: Rotary Round up 2006)
This was all 4-5 years ago and could be I was
just overlooking something - but, couldn't figure out what it was, so pulled
out the thermostat.
Ed
Sorry, I forgot about your plugs up deal. Years ago there was a sender of
some kind in the top of the center iron. I placed my water temp sender there.
When filling with coolant I could loosen that sender and almost all of the
trapped air would escape. This why I have stayed with the make up tank idea
since 1980. Some of the air will just not move out at less than full throttle.
I like the air showing up in the tank, rather than sitting beside a hot spot
killing the engine. In three heat cycles, there is no air left at all. I keep
the tank 1/3 full for the whole season. it never uses any
additional coolant. I pressurize the coolant until the cap releases after
checking coolant levels.
I forgot to say that I use 10% antifreeze in the coolant. Racing in
October can get rather cool.
Lynn E. Hanover
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