Centrifugal pumps are never "self-priming" in fact they need a net positive
suction head (NPSH) in order to operate. In other words, they don't suck. We
get away with using them inappropriately in a closed system because the
operating pump supplies it's own suction head. If you have a suction-side
surge tank that's higher than the pump then you are assured of always having
a priming head for the pump as long as the tank has water in it, so a fully
bled system is not quite so critical. Without it, if you get enough air into
the pump to make it stop pumping, it may not restart until the temperature
rises enough to force water into the pump chamber. Which could be shortly
after #4 cylinder sticks it's rings.
As a former nuke, I know just enough about surface boiling and pumps to be
amazed that these engines work at all. They need all the help they can get.
-----Original Message-----
From: owner-fot@autox.team.net
To: 'fot@autox.team.net '
Sent: 7/14/2005 6:16 AM
Subject: RE: TR3 Radiators / Thermostat Housing Rad Cap
I agree. I just discovered the suction side of the water pump link a
week
or two ago. I already have the bleeder in the thermostat housing but
was
having great difficulty getting the pump "primed" after a recent
replacement. I think my radiator is just slightly too low to get the
water
level up to the impeller. I took the plug out of the line in the pump
housing that used to go to the thermostat housing (the bypass line),
dumped
a bit of water in there and presto! Primed pump and water squirting out
of
the bleeder immediately. I even got to use my new Alexander Racing
Enterprises wrench to remove and re-install the plug in the pump.
- Tony Drews
At 07:17 AM 7/14/2005, Bill Babcock wrote:
> I think you are way better off with a bleed screw on the thermostat
housing
>and a surge tank connected to the suction side of the pump.
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