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Thanks for the replies.
Steve, that's great news on not needing an extra fill point. It'll
be a lot easier to drill/tap a 1/8" NPT hole than weld on a fill
port. And pressurizing through the overflow port is sheer genius
to this limited mind. You've saved me two or three dozen bucks,
several ounces of weight, some complexity, and a lot of
fabrication hassle.
Many thanks!
Charlie
On 1/29/2015 10:53 AM, Steven W. Boese wrote:
Charlie and Jeff,
If I am seeing things correctly, Charlie's connections to the
expansion tank are both near the bottom of the tank due to the
dip tube attached at 10 o-clock. This is essentially how I
have my expansion tank connected. I installed a Schrader
valve at the top of the thermostat housing which is the
highest point in the cooling system. My entire expansion tank
is below the level of the thermostat housing. When filling
the system, I add coolant to the expansion tank and pressurize
it through the overflow port in the filler neck while opening
the Schrader valve. When coolant is expelled from the
Schrader valve, the system is purged of air. A filler cap at
the highest point is not needed.
The expansion tank does not back-fill with coolant unless the
filler cap is released and also the Schrader valve is opened.
Both conditions are necessary for the expansion tank to
back-fill.
Having both the inlet and outlet lines connected below the
surface of the expansion tank is a good thing in my opinion.
They just need to be separated by enough distance that
any bubbles can separate upward rather than be drawn into the
outlet line. I keep the inlet line to the expansion tank
restricted for two reasons. One is that coolant circulating
through the expansion tank is bypassing the radiator and not
contributing much to cooling. The other is to limit the
pressure seen in the expansion tank. With a thermostat in the
system that is not fully opened, I see pressures in the
thermostat housing on the water pump side of the thermostat of
up to 40 psi at high RPM.
With my system, I need at least a quart of air space in the
top of the expansion tank when cold. If the air volume is
less than this, the expansion of the coolant will fill the
entire system with liquid when hot. If there is residual air
space in the expansion tank, the pressure in it will vary
continuously with operating temperature. If the
system becomes completely filled with liquid, the pressure is
constant at the relief pressure of the filler cap.
That is how my system behaves, for what it is worth.
Steve Boese
RV6A, 1986 13B NA, RD1A,
EC2
Charlie, I don’t think your system
will work as you expect and I’m pretty sure it is not
the same as the Hanover-Setup. Attached is the Hanover
cooling system diagram … note all the cooling elements
(radiator, hoses, filler bottle) are completely full of
glycol (green); only the expansion tank (approx 1 litre,
with stant lever cap) has room for air, filled only
about 1/3. The location of the expansion tank is shown
higher than everything else in the diagram but can
actually be located lower; what is important is the
connections be as shown, i.e., highest point of
saturated cooling system connects to bottom of expansion
tank, expansion tank is only 1/3 full and this is where
you install the pressure cap.
The location of your steam lines to
top of expansion tank is correct but I think with your
bottom connection going to pump inlet what will happens
is any portion of the expansion tank lower than highest
point in the system will simply back-fill with coolant
and you will no longer have an expansion tank but rather
a coolant tank. I believe your methodology will work if
at least 1/3 of expansion tank is the highest point in
the system. One thing for sure is with the pressure
sensor located on the pump inlet side, you will be
measuring the lowest pressure in the system.
Jeff
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I'm
setting up the cooling plumbing for the
Renesis (RV-7) & wanted to try the setup
used in a lot of current autos, where the
'steam' lines go to the expansion tank and the
coolant in the expansion tank is constantly
pulled back into the input to the water pump.
I'm hoping that this will do a continuous
purge, similar to Lynn Hanover's setup with
the extra swirl tank. I couldn't get the
swirl/expansion tank higher than the water
pump outlet (highest point of the system), so
I modified the hotrod expansion tank shown,
with the hope that when the system cools, it
will be forced to pull only coolant back into
the 'steam' lines. The plan is to collect the
steam lines from the radiator, flywheel end
iron, and pump outlet & return them to the
port located at the 10 o'clock position on the
tank.
I'm assuming that
I'll need to add a fill port on the pump
outlet (top of engine) and fill from there
after partially filling & capping the
expansion tank. Any thoughts/criticisms?
Charlie
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