A> Perry had a cooling system malfunction in his 290,000 mile daily beater RX7.
A> It is still to be determined what the problem really is
A> but one of the things that happened was his water pump failed
A> catastrophically.

A> A few years ago we had a heated debate
A> on this subject. Some felt that cavitation was a big problem
A> in Mazda water pumps and that the pump should be slowed
A> if you were going to run the engine at super high RPM. Perry's engine
A> briefly touched 7500 RPM for some reason not clear to me.
A> Perhaps he missed a shift.

A> "Cavitation

A> Cavitation is a phenomena which occurs when a liquid vaporizes as it passes
A> through a pump and then quickly turns back into a liquid. The collapse of
A> the vapor bubbles creates destructive microjets of liquid strong
A> enough to damage the pump. Vaporization occurs if the pumped liquid
A> drops below its vapor pressure. As a liquid accelerates through a pump it
A> loses pressure (Bernoulli's Principle). If the pressure drops below the
A> vapor pressure of the liquid then gas bubbles will instantly form as the
A> liquid vaporizes. These bubbles just as quickly collapse, causing cavitation
A> to occur. To prevent cavitation the pressure (more correctly the head) of
A> the liquid entering the pump must be high enough to prevent the subsequent
A> liquid pressure drop from reaching liquid vapor pressure"

A> http://www.pricepump.com/pumpschool/default.htm
A> http://www.corrosion-doctors.org/Forms/cavitation.htm

A> It is hard from me to believe that
A> this cavitation damage was done to his pump in an instant
A> but it did happened in a relatively short time as he changed
A> the cartridge not too long ago. I did notice that his lower
A> radiator hose on the suction side of the pump did
A> not have a steel spring in it preventing it from collapsing.
A> If the hose collapsed it could cause the pump to cavatate
A> by blocking the water supply.

A> This is by far the severest case of cavatation damage I have ever
A> seen.

A> Paul Lamar

Hi Paul,
I would suggest that he has a electrical problem with his water temp
sender in the cooling system. This can cause this type of problem and
quickly if there is stray current into the water. Check the sender.
I have found this in marine instalation before but with cast iron the
damage is not so rapid.

--
Best regards,
 ddunbar                            mailto:ddunbar@echidna.id.au

Thanks Don.

Paul Lamar
 
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