I like David's constant pressure design the best for an inverted
system. I'm not sure why the design was dropped so quickly on the
list.
    I have been trying to find a way around Aubrey's objection to the
constant "high" pressure when the engine is at rest.
    The engine is at rest for quite sometime before the liquid cools
down and retracts reducing pressure. Is this enough time to get the
o-ring shift?
     How much does a 75F to 30F then back to 75F ambient pressurize
the system? When the temp falls liquid is suck up from the A-can.  Then
the temp comes backup and pressurizes the system. Extremes happen  like
this in Arizona where 75F day and a 30F night mid winter. Summer time
might have even higher extremes. Can this produce enough pressure to
get the o-ring shift.

But, to relieve pressure at rest.....
    If we put a spring in the liquid side of the P-can as in the
attached picture (badly drawn red spring). Then charge the air side
with the upper bleeder open, so we get the air and the spring in
equilibrium. Then when the system is at rest we have a relatively
non-pressurized system.
    ?Ideally? the spring provides equilibrium in a short throw. So
that when the system starts to expand it will leave the spring  behind.
    At rest with the spring and air in equlibrimum and a ambient temp
cycle, as above, the pressure of the system should stay more constant
by allowing the system to grow without exceeding trigger point to
overflow.

--
Blake C. Lewis

The way I see it there are two major problems. As far as I can  tell  there is
no way to get dissolved air and gas out of the coolant. Second,  it  is expensive
to make as you need a large lathe. The whole idea with the Mazda   RX8 system
is to get the air out on a continuous basis.

BTW the cooling system in my RX8 appears to be far more robust than
in my RX7. From time to time the RX7 would get hotter than the   thermostat.
The RX8 never seems to do that.

Paul Lamar ...No rotor no motor.

If formation of air bubbles is a one time event as suggested by the
experiment with boiling water on the stove (sorry I forgot who did
that but it was very informative )  then, there could be a  bleed
line with  valve which would be opened only for the the initial
engine run to allow air to escape. The bleed line would not have to
be part of the floating piston can.   Jerry

It was Bill Schertz that said you had to boil the water.
After you boil the water in the block by letting the engine overheat
how do you know you have all the disolved gas out of the coolant?

Dissolved air leaves the coolent as it is heated and  before boiling
temperatures are reached.   I just tried heating water in a pan but
keeping it below boiling temp.  I don't know the exact temp because I
don't have a thermometer but it was not even simmering.  Later today
I will repeat with a thermometer.  The bubbles formed  almost as soon
as the burner was lit.  No new bubbles were formed after a few
minutes.  And as was previously reported, when the water is allowed
to cool and is then reheated, no bubbles form.    It took about 25
minutes for all the bubbles to disappear because they cling to the
pan.  If the water was being circulated, I think the bubbles would be
scrubbed away much quicker.  Steam bubbles, on the other hand, do not
cling to the pan, they rise immediately.    If  the water is heated
to a yet to be determined temp (below boiling) and held  there for a
yet to be determined time, we can be sure all the dissolved gas is
out of the coolant, at least as long as the coolant is water.  I
don't know the effect of antifreeze yet.   My apologies to who ever
did this experiment first--they deserve all the credit.   Jerry


Bill Schertz said the water MUST be "boiled".

Paul Lamar

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