Water Pump Cavitation

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The_Nuke

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Cavitation around the water pump has always been something I knew was "a thing", but i'd never seen it affect anyone's engine i'd ever worked on. Well now I can say I have seen its effects for real, and it was in my own engine as it so happens.

The engine is a 2012 5.7L Hemi in the Charger in my signature. The coolant was apparently the factory fill, and that is the main culprit to why the cavitation started to occur I believe.

There were no other symptoms to indicate an issue was occurring. I just happened to find this when replacing the water pump and other coolant system parts as part of the engine's maintenance services.

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I really can't tell exactly with the pics on my computer. I would guess electrolysis or rust.
 
Originally Posted by CT8
I really can't tell exactly with the pics on my computer. I would guess electrolysis or rust.


It's an aluminum plate that the damage has started on. Seems to me like cavitation is the most likely culprit.
 
Pressed sheet metal impeller ?

Always find a pump with a closed back cast impeller IMO...when doing testing on Holdens years ago, the pressed tin moved nearly no water at idle, and could not maintain a head difference between two buckets.

The cast ones could...and didn't leave cavitation pits.
 
From what I know this is not common on the well produced, for many many years, 5.7 Hemi. There must be an underlying factor at work here. Does the radiator cap pressurize the system properly? A lack of pressure can certainly contribute to a cavitation issue. Any other cooling system modifications? any pulley modifications? Lower radiator hose collapsing? Does it still have a thermostat? Was this the factory water pump? Some after markets have different style impellers that could create issues.
 
Yowza

Lot of high RPM driving?

How's the radiator cap? Aside from raising the BP, the added pressure is designed to mitigate cavitation
 
Originally Posted by The_Nuke
Originally Posted by CT8
I really can't tell exactly with the pics on my computer. I would guess electrolysis or rust.


It's an aluminum plate that the damage has started on. Seems to me like cavitation is the most likely culprit.



I'm by no means anywhere near one of the smarter members on the board, but electrolysis likes aluminium. It will always erode aluminium, but more commonly where coolant turns corners in coolant passage ways. But it can be anywhere.
 
Last edited:
Plastic or fiberglass impeller. Has a flat back that faces the aluminum cover this damage is on. The blades are on the inside of that flat surface.

Originally Posted by Shannow
Pressed sheet metal impeller ?

Always find a pump with a closed back cast impeller IMO...when doing testing on Holdens years ago, the pressed tin moved nearly no water at idle, and could not maintain a head difference between two buckets.

The cast ones could...and didn't leave cavitation pits.
 
Originally Posted by KneeGrinder
Originally Posted by The_Nuke
Originally Posted by CT8
I really can't tell exactly with the pics on my computer. I would guess electrolysis or rust.


It's an aluminum plate that the damage has started on. Seems to me like cavitation is the most likely culprit.



I'm by no means anywhere near one of the smarter members on the board, but electrolysis likes aluminium. It will always erode aluminium, but more commonly where coolant turns corners in coolant passage ways. But it can be anywhere.


I would have expected to see it eat a hole in the heater core before it could do this much damage to that cover.

Also I did an electrolysis test by sticking the DMM lead in the coolant with the engine running and did not get an out-of-bounds result.
 
Lots of high RPM driving.

No coolant system modifications.

Coolant had > 120K miles on it and was > 70 months old.

No visiaul signs of problems with cap. Cap is not OE; I know, I know, get an OE one. I will. But they don't sell them after 7pm, it's a state law I think, so the cap will remain non-OE for a few days while I wait on one to be delivered.

Replacing pump, stat, all hoses except engine oil cooler hoses, ECT sensor, and half the associated pulleys (other half got replaced upon acquisition of vehicle in June), and of course coolant.

Using 7.0 quarts of Zerex G-05 and 8.3 quarts of Nestle Splash zero calorie flavored water. Orange flavored to be specific, because it's my favorite flavor, and I figure the citrus in the water that gives it its flavor will do double duty as a flushing agent to get anything left behind from old coolant.
 
Originally Posted by The_Nuke
Originally Posted by KneeGrinder
Originally Posted by The_Nuke
Originally Posted by CT8
I really can't tell exactly with the pics on my computer. I would guess electrolysis or rust.


It's an aluminum plate that the damage has started on. Seems to me like cavitation is the most likely culprit.



I'm by no means anywhere near one of the smarter members on the board, but electrolysis likes aluminium. It will always erode aluminium, but more commonly where coolant turns corners in coolant passage ways. But it can be anywhere.


I would have expected to see it eat a hole in the heater core before it could do this much damage to that cover.

Also I did an electrolysis test by sticking the DMM lead in the coolant with the engine running and did not get an out-of-bounds result.

Consider what cavitation means and why I would occur at the water pump vs. any other areas of the system
 
I am going to assume on the flavored water that your kidding. But this is classic metal erosion caused by cavitation, and something I rarely see outside of the marine world. Hard to tell by the pics, but does this plate / cover get replaced ? If its easy to replace, then by all means do- the pitting is only going to compound the problem.
 
Originally Posted by rubberchicken
I am going to assume on the flavored water that your kidding. But this is classic metal erosion caused by cavitation, and something I rarely see outside of the marine world. Hard to tell by the pics, but does this plate / cover get replaced ? If its easy to replace, then by all means do- the pitting is only going to compound the problem


I was not kidding, orange really is my favorite flavor of that Nestle bottled water!!
 
Look like poor aluminum casting which left bubbles in the final product and the cavitation eroded it away exposing the bubbles.
 
Originally Posted by FordCapriDriver
Improper coolant can also cause cavitation issues.

Yes, and proper coolant that has exceeded its serviceable life in both age and miles makes it improper IMO

Originally Posted by Silk
Missing pressed steel impellor blades are usually cavitation, not corrosion as most think it is.

My water pump was missing steel impeller blades for sure...although, it still has its plastic or fiberglass impeller blades fully in tact:
[Linked Image]
 
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