Here are the essentials.

             --
             Paul Lamar ...No rotor no motor.


         Paul,
         How would you purge air out of the system in this
    arrangement?  I know
         that this has been discussed in detail in the past, but it
    seems that
         you would need a line from the rear side housing to the
    pressure can in
         order to purge air that may be trapped in the engine.

         Mark S.

         You must run a vent line from the highest point in the system
         to the top of the pressure can. In a tractor tail dragger it
    would be
         the rear (car) end housing. The housing closest to the PSRU.
         The best place is where you have the pressure fitting now. I think
         it is the return line from the water heater port in the stock
         RX7 system.

         The pressure container must be mounted as high as possible.
         The cooling system is constantly generating tiny steam
         bubbles. These must be able to rise to the highest point in the
         system which should be just below the pressure cap. When the
    pressure
         in the system rises to the blow off setting of the pressure cap
         this steam accumulation will be the first thing purged to the catch
         can.

         Paul Lamar ...No rotor no motor.

    Paul,
    Yes, wp-plumbing5.jpg shows it more clearly.  I didn't see that line in
    the previous jpg.

    On my installation, the radiator is angled from front (highest) to rear
    (lowest), so I have a 1/4" line going from the upper most tank back to
    the pressure/swirl tank.

    One caveat, when filling the cooling system, it is possible (likely) to
    get an air pocket in the vicinity of the wp impeller.  In my
    installation (20B, thermostats removed), running the engine will
    not purge the air from this area.  You must remove a plug from the side
    of the wp housing and continue adding coolant until liquid runs out the
    hole.  Then replace the plug, run engine and coolant should circulate.
    An easy way to tell if it is circulating is to hold your hand on the
    outlet from the wp after the engine has been running for a minute or
    two.  If it is warm/hot, water is circulating.  If it is still cold,
    there is no circulation.  It is my understanding that more than one
    engine, following rebuild, has been fried due to this scenario.  It may
    not be a bad idea to install a petcock on the side of the wp housing
    for
    the purpose of purging air when refilling the cooling system.

    Mark S.


Instead of reinstalling a plug in the side of the wp housing, would it
be worthwhile to run a purge line from there to a high point in the
system?  I guess it might depend on how tough the plug is to get to once
everything is installed on the engine..


Matt-

Here are some water pump pictures. Perhaps Mark S can mark
them up using MS paint for us. The 13B Cosmo pump and the 3 rotor
pump are the same. Note the bleed hole at the top of the
pump cavity.

Paul


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