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When water and coolant in your engine heats and expands, air bubbles are formed from localized boiling. The general term we often use is cavitation. The scientfic term for that specific localized boiling I mentioned is nucleate boiling. – I can’t believe I found a picture of this! These bubbles collapse or explode against the outside of the cylinder liners and take a portion of the steel with it. This is called cavitation erosion. These little bubbles are imploding at the cylinder liners at pressures up to 50,000+ psi. They start blasting into the cast iron liner and causing a “pitting process” that continues over and over until they tunnel their way into the combustion side of the cylinder. If coolant enters the combustion side of the cylinder you’re looking at an engine rebuild with a bore and resleeve job.

Enter SCAs - Supplemental Coolant Additives – recommended maintenance for your Ford Powerstroke cooling system. What they are in a nutshell is a liquid poured into your cooling system at a recommended interval. A chemical reaction caused by heat and metal contact causes the liquid to become a solid "scale" as it coats the outside of the steel cylinder liners. This "scale" creates a sacrificial liner that is removed by the tiny explosion of collapsing bubbles instead of the steel cylinder liner. So the theory is that the pitting of the liner won’t occur. In order to replace the void and the displaced scale that was removed upon implosion, you must have residual unconverted SCA (liquid form) still floating around in the system. The displaced scale is now an abrasive partical floating around in your system which stays there until flush time. All the while these little pieces of abrasive scale are wearing at water pumps, hoses, insides of radiators, etc.

The balance of SCA is important because you want enough additive to keep replenishing the sacrificial layer, but not so much that you have tons of fallout that will cause accelerated wear on the water pump and clogging of passage ways, thermostats, etc. The "plus side" to SCAs is that they protect your engine from cavitation. The downside is that the additive is not discriminative. It will coat ANY metal. It sticks to your thermostat, inside walls of your radiator, water pump impellers, etc. It doesn’t know the difference between a cylinder liner or water pump impellor. Everything is going to get coated - including the scale that already exists. It begins to "clog the arteries" of your system. There are several small passageways through the cylinder heads and blocks that are piling layer upon layer of scale until they are restricted or completely closed off. To make matters worse, the coating acts as an insulator. So while the coolant continues on its path and stays at normal operating temperatures because of the thermostat and the radiator, your cylinders and cylinder heads can be running at greatly elevated temperatures because the heat won’t transfer through the layers of scale. Less than 1/16th of an inch of scale coating will reduce the heat transfer ability by up to 40% according the Penray. The more you overdose the system with SCAs, the thicker this coating becomes. Cylinder temps grow even hotter, this causes more cylinder wear and piston scuffing but your water temp remains in "normal" range. In this situation, your engine can actually be overheating internally and causing damage while your water temperature remains normal. You would never even know it.

Why would we use it then? This technology is older than dirt. Let's just put wooden wheels on our trucks. We do it because we are told it is what we need to do to protect our system. Most would never even question the use of SCAs.

Coolant technology has changed drastically in the last ten years. Some use OAT (Organic Acid Technology) coolants like what is used in GM products - red stuff. International uses it in there newer engines as well. No additives are needed as they are pre-charged with a special inhibitor package. Ford still says you cannot use it in Ford engines because of seal incompatibility. Ford now has Premium Gold like those used in the 2002-2008 Trucks. While the interval change of the Premium Gold is 100,000 miles, you still mix with water and it still has the properies of a conventional coolant. Cavitation and other water caused problems are still going to exist. Corrosion, scale buildup, and rust can still occur. Again you are not eliminating cavitation, you are preventing cavitation erosion. No additives are needed because of the special inhibitor package and it is safe to use in all Fords. The Gold works just like the OAT, but is a different chemical base. For pre-2002 trucks that switch over to Premium Gold from the green stuff you must remove every bit of the green coolant from your system. If there is any green at all you must follow the interval changes recommended for the green.

Evans NPG+ is what I run in all my vehicles. I have carried this product for 7 years now. It is good for 500K miles with no additive use. It has no water in the mix and without water it cannot rust, cannot allow corrosion of any kind, and will not exhibit cavitation since there is no water to boil. It doesn't protect the engine from cavitation –cavitation just doesn't exist in an engine running Evans. The boiling point of Evans is over 400 degrees. I wouldn’t run anything but Evans NPG+.

If you MUST run conventional green coolant eliminate the SCAs by using RMI-25. It creates an organic coating, which when broken loose does not create a solid abrasive particle, cannot create an insulation barrier, and has no ill effects with an overdose situation. It is a cleaner, conditioner, lubricant and something called an "oxygen scavenger". This helps to keep cavitation from ever existing. The cool thing is that RMI-25 actually removes the SCAs you’ve already put into your system completely, even the hardened deposits. Cooling system components look brand new after 9+ years of use. I've seen it! Again, the coolant filter system better be on your truck to trap all the deposits and scale that the RMI-25 removes.

On a side note: Guys with increased HP trucks should be looking in to an upgrade to Evans NPG+ in place of a conventional coolant. Higher temperatures created in the cylinders from the increased HP can create a brief moment where the cylinder/piston relationship becomes too tight and they end up throwing a rod. There’s so much money in the engine, but so little spent protecting it. And while you’re at it – dump the petroleum oil and get some synthetic in there. Protect your investment. AMSOIL and EVANS NPG+.


View my Coolant Article written in 2001 discussing coolant choices and introducing RMI-25 and Evans NPG+ here.

 

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Bob,

Good info, but I would like to add that at least for the 7.3L it doesn't have the typical steel liners like on a lot of other engines, it's a parent bore engine w/o liners steel or otherwise. The only real cavitation issues I've read about are for the 7.3l IDI engines that were apparently 6.9L bocks bored out and had much lighter metal between the cylinder walls and the coolant passages and suffered significant cavitation issues. I'm pretty sure the Cummins 5.9L which also uses the same HOAT coolant as the Ford Gold is also a parent bore engine.

Larry
 

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Larry,

Thanks for the input on the article! You definitely bring up an arguable point, but this article was written to address the different ways in handling cavitation. As we all know, the Ford manual and IH tell us we must protect the engine and cylinders from cavitation and their effects. We are not debating with Ford whether or not cavitation erosion exists in the 7.3L powerstroke. The point of the article is to introduce effective ways to prevent erosion or the effects of cavitation, and if you feel it is an issue, even better ways of doing it than SCA’s. My main focus was on damaging effects of the actual SCA’s more than anything.

Bob

 
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