> > .Tracy and others, what is the theory behind so much liquid in the
> external
> > expansion tank? Thermal expansion of the initial coolant volume doesn't
> > account for such a large overflow. So is vapor building up inside? If it
> is
> > there is no longer a liquid filled system. I don't get it.
> > Peter
>
> I'm not 100% sure what is going on but I think you would be surprised how
> much the 50-50 coolant expands with heat.  I flight tested the new bottle
> yesterday and verified that on cooldown the system was completely topped
off
> with coolant (no air at top of fill port.) This was never the case before.
>
> This also accounts for another anomaly I've noticed over the years.   It
> seemed like the water cooling was slightly better on the first flight
after
> topping off the system.  I was never sure because the next flight was
> usually on a different day, different temperature, humidity, etc.  Now
that
> I've been paying close attention I have verified that only a few ounces
> worth of air in the system makes a noticible degredation in cooling
> performance  (about 5 degrees worth).   Not sure why this is happening
> either but I'm happy with the results.  With more experimentation the
answer
> will probably come out.
>
> Tracy Crook

Yes, Ed, I agree with that explanation of the heating process but...
If we put a pot of coolant on the stove and heated it to 190 I'd bet that
the 7 or 8 litres  wouldn't expand more than a couple of percent. Tracy
aren't you seeing more than 10% expansion? We'd see vapor coming off which
would be captured in our contained system. So if the thermal expansion is
less than what you are getting in the overflow bottle doesn't there have to
be vapor in the system?
Peter.