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Message
I'm currious if this will work,
or if I will get air to the wrong places.
Hi
Chris,
I would suggest that you use
a tank, mounted to the top of the firewall if possible, so the fill cap will be
the highest location. It's not a show stopper if you can't put it there,
but it will make filling the system much more difficult if the fill cap isn't
the highest point.
The tank would have the pressure cap, with it's
overflow hose going to the bottom of any old overflow jug. It would
also have two other small nipples for hoses. One would be at the very
bottom of the tank, and would connect to the hose you labeled as "bottom of
overflow tank". The second nipple in the tank would be near the middle
(top to bottom). This would connect to the hose you labeled as "top of
overflow tank".
The idea is to use this pressurized tank to removed all
the air from the system, and it's the way Mazda did it on the FD. The two
hoses in your picture are connected to opposite sides of the water pump, so they
aren't at the same pressure. When you connect these both to a tank,
there will be flow through the tank. Since this bypasses the radiator, you
don't want these to be very big.
What happens is the water (with air bubbles) flows from
the top of the system, into the middle of your tank. The air bubbles go
up, and the coolant goes down. The return flow to the engine goes out the
bottom hose in your tank, so nothing but coolant is returned. The air is
collected at the top of your tank, where the pressure cap is. During
normal heat cycles, the air will get pushed out into the overflow jug, and
coolant will get sucked back in when the engine cools.
BTW, Mazda called this (amazingly enough) an "AST" or
Air Separator Tank.
The AST tank doesn't have to be large. Even a
pint would do, but I'd try to go a bit larger than that. Taller rather
than wider would be a plus as well. The plastic overflow jug should
be at least a quart, or better a quart and a half.
Cheers,
Rusty (hanging heavy expensive object on the nose
now)
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