I'm big into oil filtration but have never gone into the coolant side of it. Looking at things from both sides:
Like enhanced oil filtration, at the end of the day, the difference in longevity between good STANDARD maintenance practice, i.e. regular service, is minimal and is often not cost-effective. I have not crunched numbers with coolant filtration, nor seen any long term test data on the benefits (please don't attach sale pitches as test data), but I have with enhanced oil filtration and the only way you can make that be cost-effective for the average Joe is to run much-extended OCI (Oil Change Intervals). In other words, enhanced oil filtration is more an oil life enhancement tool than engine life enhancement, versus good standard filtration and maintenance. If you drive the normal 15K a year, you make it pay by doubling or tripling the OCI. There is an engine life extension benefit but it's way out at the far end. Most trucks die of other causes or change owners before that benefit kicks in. If you crank on a LOT of miles per year, the life payoff comes sooner or if you intend to die of old age in the truck. According to statistics, there is a big arc in the longevity/wear curve when if comes to the size and amount of contaminant particles. Within the realm of "normal" oil, oil filtration and standard OCI, the curve is pretty flat and the extra cost of enhanced oil filtration (small particle bypass filtration) takes a very long time to recover. Not changing the subject here, just giving you an idea of my methodology in thinking about this.
Back to the topic at hand, I surmise the same rules apply to coolant filtration. If you can significantly extend coolant life, then you can easily make it pay, especially given how easy and relatively cheap it is to install and maintain one. Thing is, though, modern long life coolant can last 100+K miles anyway. Is there some enhanced benefit within that 100K mile period? Thinking logically, once you get the casting sand out of the cooling system, there are few (pretty much no) contamination inputs to add anything harmful. Akin to an automatic transmission, the most important time is right after the build, or rebuild. Once the system is clear, there is nothing left in a closed system to cause a problem, assuming you installed good water. Are silicates in the coolant a filtration issue? Does material slough off the water jacket? Do they do so in amounts sufficient to cause problems? Don't know the answers to those questions but thats where I would start researching.
The second place to research is, what are the benefits? What difference does it really make if a little contamination is flowing around the system? What fails as a result? Water pump? Maybe but there are many other nonrelated causes of water pump failure, many of them connected with neglect, past or present, and many not related to the coolant at all. Or out of balance fans. Or belts too tight. Or too loose. Has someone run tests to see what level of coolant contamination is required to cause early water pump failure, then done tests to see how long a water pump with last with perfectly clean coolant?
Probably the best part of the idea is that it's a pretty cheap addition. I'd make it a priority on a new truck or one that is fresh from a rebuild or a repair involving something that can allow contamination to enter the system (chunks of RTV, rust flakes, metal, gasket pieces, etc.). If the truck's had a couple of coolant flushes (good one, not half-assed) it would be less a priority.
As an aside, my practice after rebuilds is to just add water the first time, maybe with just a rust inhibitor. Run that for a short while then dump as much as possible, flush and then nstall the coolant. If there are leaks or issues with the rebuild early on, then you don't have to worry about wasting or trying to save expensive coolant as you fix them. You get the issuers sorted out then install the final load of coolant and additives.
All that said, anecdotally, I've had my '86 truck since it had 7K miles. In the early days, I ran 2-3 years on a load of coolant, flushed and changed it. Later, as coolant improved, I stretched it out to 5 years or so and starting adding the SCAs in the mid-'90s. When I tore the engine down in 2009, I took note of the fact that the water jackets were grey metal inside. No rust, no scunge. I didn't find any casting sand but the block was THOROUGHLY cleaned inside and out, so I doubt much, if any, is left after all that. I should probably hook up a filter to test that hypothesis. I have never worn out a water pump on this truck. I replaced the original 80 GPM unit with a 100 GPM pump for the enhanced cooling because I used to tow very heavy but when I hit a deer shortly after moving to Ohio, that pump was damaged and I couldn't replace it. It has a standard flow Ford reman on it now that's about 12 years old.
I have used various "water wetter" type things, currently Royal Purple's Purple Ice ( I have nothing useful to report about it good or bad) and between it and Fleet Charge in a 50/50 mix with distilled water. I haven't felt a strong need to add coolant filtration to the mix. Someday, maybe.
