<snip>

The pump damage you see in the first picture here was caused I think by
running the water level low for awhile at high RPM. It is the only
explanation I can come up with. BTW it is also perhaps where the
Mazda pump cavitation myth started. We will know more about this if
Vance's 3 HP pump test rig is successful at pumping water
at 7000 or 8000 RPM.

The reasons most pumps have been mounted high in the last 100 years is
so they could mount a cooling fan on the same shaft and drive it with
the same belts. This no longer applies as most engines now use electric
cooling fans.

Paul Lamar

A couple of questions (well 3).  Why is the bleed hole shown in
water-pump2.jpg needed?  Any reason it would be needed on the new
castings?

I am not sure about that Bob. I have no real certain idea.
I cannot read the Mazda engineer mind on that one.
Could be just a bleed hole for fully filling the system.
You can simulate it by running a small hose around the inlet to the
outlet. Try it without as in my test I noticed no difference.

The  original pump was drawing cooled water from the radiator but the
new pump is drawing hot water from the engine.  Any reason to think the
higer operating temps would be detrimental to the pump?

Thanks,
Bob White

http://www.bob-white.com
N93BD - Rotary Powered BD-4

No not true. The inlet to the pump is from the outlet from the
rad. Here is the old and the new 3D on the plumbing.
The new 3D does not show the pump inlet connection but it is
the same as the old 3D. Mounting brackets are also not shown.
 
Paul Lamar
 
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