Gas Engine cavitation

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Hi all:

I recently became aware of the phenomenon of cavitation in cooling systems. I have done some searches on gasoline
engines, but only found info about diesel engines. Apparently, it's common with diesels.
The reason why I ask is because I have long preferred running my cooling systems unpressurized on my gas cars.
The last two cars I have ran unpressurized were two Crown Vics. They both tolerated being unpressurized in regards to
not blowing coolant out of the degass bottle. They both spent their time in service almost exclusively unpressurized.
Both cars are gone now. One suffered from old age fall-apart, and the other was totaled.
After reading some articles, it seems that cavitation is reduced somewhat by system pressurization. I'm aware that
cavitation affects the water pump impeller, and to a lesser extent at cylinder walls(much less so for gas engines).
Also, I think that coolant formulators use types of SCA additives to minimize the effects of cavitation.
In both previously mentioned cars the engines never experienced a cooling system failure. I changed the coolant
every 2 to 3 years. So, from my experience with the two cars I had mentioned, nothing detrimental had ever occurred.

I more recently installed a new radiator cap on my 5.7 Hemi Charger. I drilled a pin hole into the center of the
cap to relieve the pressure. So, it now runs unpressurized as well.

So, getting to my questions.
Has anyone else done this? I don't know of anyone else who has done this.
Any thoughts if cavitation is a significant issue in gas engines?
 
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....I have long preferred running my cooling systems unpressurized on my gas cars.
Can I ask why?

Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block. Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.
 
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If the cooling system isn’t maintained with the appropriate coolant and cap, cavitation is a real thing.
 

PaxilPlease

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Can I ask why?

Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block. Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.
You certainly can ask.
To greatly reduce the chance of catastrophic blowout of a hose, leaking at factory tees and other connectors, prevent radiator leaks, help reduce the possibilty of causing a head gasket to leak, etc....
 

PaxilPlease

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If the cooling system isn’t maintained with the appropriate coolant and cap, cavitation is a real thing.
I agree. However, I haven't seen any reports of of it happening to gas engines. Seemingly only diesels.
 
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Why on earth would you negate the entire purpose of a pressurized radiator cap in a pressurized system? You might as well just stick a shop rag in the radiator instead. It is under pressure for a reason. If it was better without pressure, i'm sure most cars would have been run that way for decades now. Why have a solution if there is no problem?
 

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I've seen nucleant boiling destroy aluminum heads in fairly new cars. This is on the suction side of the cooling system. Not letting the system pressurize exacerbates the problem.
 

PaxilPlease

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Why on earth would you negate the entire purpose of a pressurized radiator cap in a pressurized system? You might as well just stick a shop rag in the radiator instead. It is under pressure for a reason. If it was better without pressure, i'm sure most cars would have been run that way for decades now. Why have a solution if there is no problem?
Shop rag in the radiator? Huh?
 
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cavitation creates micro bubbles that reduce cooling capacity. If you put a heavy load on it you may have issues. Unless you have a leaky rad or heater core no reason to run unpressurized. When i was 20 i had a car with leaky radiator tube i sealed with bondo. Ran unpressurized without issue till i upgraded.
 
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Pressurizing raises your boiling point, and prevents cavitation, which would be a bigger issue on water pump impellers on a gas engine, although blocks & heads can have problems too. I shudder to think what Dexcool or similar OAT coolant would do with an unlimited supply of air available… :eek:
 
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I would stay away from mountains or even higher elevation areas with an open system too-the higher pressure improves water pump efficiency, and the lower atmospheric pressure will cause boiling & evaporation even more quickly. What exactly are you trying to accomplish by not sealing the cooling system? Does something need replaced/repaired?
 

PaxilPlease

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I would stay away from mountains or even higher elevation areas with an open system too-the higher pressure improves water pump efficiency, and the lower atmospheric pressure will cause boiling & evaporation even more quickly. What exactly are you trying to accomplish by not sealing the cooling system? Does something need replaced/repaired?
Read my reply to WileyCoyote. Also, in my original post I mentioned that I did this before twice on 2 Ford CVs. One had close to 300k miles
 
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I agree. However, I haven't seen any reports of of it happening to gas engines. Seemingly only diesels.
I’ve seen pitting in the water pump cavity of neglected engines. Supposedly, the MO behind the Japanese OEM love of phosphates in their coolant is to provide fast-acting protection against cavitation without the abrasive effects of silicon.
 

PaxilPlease

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Pressurizing raises your boiling point, and prevents cavitation, which would be a bigger issue on water pump impellers on a gas engine, although blocks & heads can have problems too. I shudder to think what Dexcool or similar OAT coolant would do with an unlimited supply of air available… :eek:
Question about the OAT stuff. Would the Supertech of a few years ago be considered OAT?
 
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I shudder to think what Dexcool or similar OAT coolant would do with an unlimited supply of air available… :eek:
OATs take time to passivate metal. Hence why the Japanese use pHOATs and a similar story with the Germans/Ford with G-05/40/48 and Specialty Green/yellow(Prestone Cor-Guard). Which are SiHOATs, or an 2-EHA/decoanate take on a pHOAT.
 
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