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Message
Al, Rusty and
others.
I've been a little
confused with the set- up recommended. Do you have a pressure cap on the
Radiator as well as the Expansion tank and do you have an overflow bottle
attached to the expansion tank.
I've also seen where
the rad pressure cap is not on the rad but on the return to the pump.
I'm not sure how
I got dragged into this
:-)
Take a look at
the system that Mazda used on the FD. It's a pretty good system, give
or take the plastic parts. Hmmm, I wonder if the RX-8 uses the same
system. Anyone know?
As I understand
it, the point is to get all the air out of the coolant loop. The FD
actually has two pressure caps, though only one has a pressure relief valve in
it. The one without the valve is simply a filler cap, and is located
at the high point of the system (WP housing outlet on the FD).
The one with the
pressure relief valve (normal radiator cap) is located on top of a small tank
that is appropriately named the "Air Separator Tank" (AST). This tank
has two small hoses, which flow coolant through the tank all the
time. One hose comes from the output of the water pump, as high as
possible in the engine. It runs into the AST, about half way between top
and bottom of the tank. The other AST hose goes out the bottom of the
tank, and to the inlet side of the water
pump.
The idea
is to take water from the high point in the engine, where air would tend to
collect, and send it to the middle of the AST. When it goes in, the air
rises to the top, and the liquid stays at the bottom. Since the other
hose is on the bottom, only liquid is returned to the
engine.
The cap on top of
the AST has a pressure relief valve, with a hose that goes to the
bottom of a basic overflow jug. When the engine warms up, any air that was
collected in the top of the AST gets pushed out to the overflow jug. When
the engine later cools, coolant is sucked back in from the overflow
jug. After a few cycles, all the air will be purged, and it will stay that
way unless the system leaks, or needs to be drained for some other
reason.
Keep in mind that
there are any number of ways to make a functional cooling system. All
you've got to do is seal the pressure, and remove the air. Simple
:-)
Cheers,
Rusty (wishing it
was summer here, rather than
winter)
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