Jerry Hey wrote:

Looking at Lynn's drawing of his cooling system, there are two radiator
caps, one on the swirl pot and one on the catch can.  This leads me to
wonder what kind of pressure the catch can will see. On my Nissan and RX-7
the catch cans are vented to the atmosphere.  Clearly I am missing
something. Jerry

The swirl pot has a filler cap that seals the pot but does not interfere with
air or water moving to or from the make up tank. Only the make up tank (stock
Mazda) has a pressure cap. The overflow from the make up tank in my case must
end up in a container of at least one quart volume in order to keep fluids
off of the racing surface. In an aircraft, just a hose out of the cowling
would do. Exit the hose in front of the pilot and you will be the first to
know of a problem.

The make up bottle is kept 1/3 full of coolant. After several runs to temp.
the bottle will need more coolant as the bubbles are removed from the system
and are replaced by coolant from the bottle. This is not new thinking. It
came stock on my 73 RX-2.

Lynn E. Hanover.

Just the opposite on my 1988 RX-7.  The pressure cap is on the rad and the make

up tank cap is just plastic plug that is push fitted.  Any pressure in the
make up tank would blow it off.  There is a tiny pin hole vent in the
plastic cap. The older RX-7s must have had stronger make up tanks then the
little plastic one in my car.  I think it would become a grenade at 24 lbs
pressure.  Jerry

 
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