RMI-25 as SCA in a Diesel

[Langanobob]

I have a 7.3l Diesel in a Ford pickup. The high frequency vibrations from the Diesel combustion can cause coolant cavitation which in turn can cause cylinder wall erosion. Worst case it eventually eats all the way through the cylinder wall. Ford and other manufacturers recommend a Supplemental Coolant Additive that protects against cylnder wall erosion. I believe that these SCA's protect by forming a sacrificial coating, i.e., the coating is eroded instead of the cylinder wall.

The manufacturers of RMI-25 recommend it as an SCA for Diesels and claim on their website that their product contains an oxygen scavenger to prevent cavitation. It evidently is supposed to prevent cavitation altogether, not just protect against the effects of cavitation like other products. I'm not a chemist, can someone explain how an oxygen scavenger prevents cavitation?

RMI-25 seems to have a good reputation and I don't doubt that it's an effective cooling system cleaner. What I don't want to do is find out the hard way that it's not an effective cavitation preventer.

Thanks,
Bob

 

[bullwinkle]

Closed system in a newer 7.3, or open system in an older IDI? Not sure it would be possible to keep all oxygen out of an open system.

 

[Donald]

On my Ford 6.7 diesel, they recommend testing each of the coolant systems (there are two) and adding the Ford additive if indicated.

That's my advice.

I think RMI-25 is good stuff, but my use is for cleaning old cooling systems. The Ford additive cannot be very much money.

The dealer basically said it usually works out the additive is needed half way through the coolants life.

 

[Langanobob]

Originally Posted By: bullwinkle
Closed system in a newer 7.3, or open system in an older IDI? Not sure it would be possible to keep all oxygen out of an open system.


It's a newer '96 Powerstroke, if 1996 qualifies as newer. Assuming the oxygen scavenger works, how does a lack of oxygen prevent cavitation?

 

[Fred_Garvin]

You have a parent bore block so there is no danger of cavitation.


Originally Posted By: Langanobob
Originally Posted By: bullwinkle
Closed system in a newer 7.3, or open system in an older IDI? Not sure it would be possible to keep all oxygen out of an open system.


It's a newer '96 Powerstroke, if 1996 qualifies as newer. Assuming the oxygen scavenger works, how does a lack of oxygen prevent cavitation?

 

[Chris142]

actully cylinder wall cavitation is common on his 7.3 power stroke if the wrong coolant is used.

 

[Langanobob]

Donald, good points and In my case, the testing is kind of a subjective nuisance. The test strips aren't cheap and have a shelf life. I'm not color blind but trying to interpret various shades of purple isn't high on my skills list.

The Ford dealer here is worse than useless, can't take it there.

Part of the RMI-25 attraction is their claim that you just add some every 15,000 miles, you don't have to test or be concerned about overdosing it.

Bob

Originally Posted By: Donald
On my Ford 6.7 diesel, they recommend testing each of the coolant systems (there are two) and adding the Ford additive if indicated.

That's my advice.

I think RMI-25 is good stuff, but my use is for cleaning old cooling systems. The Ford additive cannot be very much money.

The dealer basically said it usually works out the additive is needed half way through the coolants life.

 

[Fred_Garvin]

Anything is possible but of the thousands I have seen or worked and driven several to 4-500k miles I have never seen one perforate a cylinder. If they do It is more likely an issue with inadequate maintenance.

Why not just flush and go to a lifetime coolant that is OAT or HOAT?


Originally Posted By: Chris142
actully cylinder wall cavitation is common on his 7.3 power stroke if the wrong coolant is used.

 

[Langanobob]

Fred, the plot always seems to thicken exponentially - allegedly there is an issue with 7.3l injector cup material compatibility and OAT coolants. Not sure that's true but I don't want to find out the hard way.

All these complications are what makes the RMI-25 seem like an attractive solution, if it indeed works. You guys have a reputation for being pretty bright and so far it seems no one has been able to answer my original question about oxygen inhibitors preventing cavitation so chances are RMI-25 is a good cleaner but does nothing to eliminate cavitation.

Thanks,

Bob

Originally Posted By: Fred_Garvin
Anything is possible but of the thousands I have seen or worked and driven several to 4-500k miles I have never seen one perforate a cylinder. If they do It is more likely an issue with inadequate maintenance.

Why not just flush and go to a lifetime coolant that is OAT or HOAT?

 

[Fred_Garvin]

I assume you have a DI engine and not an earlier one.

Have you seen or experienced corrosion of the injector cups or seals on the 7.3? I would love to see some documented information on this as I have seen corroded cups on other makes but no one has been able to determine a cause.

 

[Langanobob]

Fred,
I own a 7.3 but I haven't had any problems yet. Not being a tech or working in a shop I don't have any direct experience with 7.3l motors other than my own. Google comes up with a lot of references to coolant/injector cup material and sealant incompatibilty but I haven't personally witnessed any of it. The factory evidently changed to stainless steel cups in early 1999 to avoid the problem.