----- Original Message -----
Sent: Saturday, December 10, 2005 10:03
AM
Subject: [FlyRotary] Re: Radiator
Expansion Tank
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)