Folks -
I could use some help for coolant suggestions. I have 2010 Flex with the 3.5L Ford Ecoboost engine. This is the second engine in the car (remanufactured engine by Ford) as the original engine was destroyed due to catastrophic failure of the water pump dumping coolant into the oil pan (it's chain driven for anyone not familiar with the design). When this happened to me, I suspected that the premature water pump seal failure could have been caused, in part, by a change by Ford in it's coolant recommendations starting in mid-2009 from their Motorcraft Gold to the Motorcraft Specialty Green coolant as shown in this application chart:
https://www.fcsdchemicalsandlubricants.com/main/quickref/coolantsEN.pdf
I want to avoid another water pump failure, with now about 40k in the new engine, and I am specifically interested in fact based recommendations for coolants that will have the best odds of preserving the water pump seal (both compatibility and lubricity) for these Ford engines. I am also interested in recommendations for a coolant filter for this engine in case some of the damage could have been caused by dirt particles in the system (casting sand, rust, etc.). The cooling system is designed as a sealed system with a flow through Degas bottle to help burp the system, which could lend itself to the use of a small inline filter at the pressurized feed line to the Degas bottle.
For comparison purposes, and due to the longer history of the vehicle/engine, we will look at Ford's coolant recommendations for the Taurus which uses the same drivetrain as the Flex and followed the same coolant recommendations. Early 5th gen Taurus' with the 3.5L Duratec engine have been noted to make more than 200k miles on the original water pump, presumably with the Gold Coolant (said to be the same as or similar to G-05). Starting in mid-2009, a change over was made to the Specialty Green coolant (said to be the same as Mazda FL-22 coolant) and it appears that this is the start of the trouble with these pumps and seals failing prematurely. Of note, Mazda which has used the Duratec engine in many of it's vehicles with their FL-22 coolant, has also had history of premature water pump failures. Evidence of these points can be determined by a quick Google search.
Here is a great video of the earlier and later Ford 3.5L Duratec and Ecoboost water pump design revisions showing the apparent seal failure leading to failure of the pump and catastrophic failure of the engine:
https://www.youtube.com/watch?v=yrmH4S2_ZOI
I suspect that Ford may have realized they had a seal compatibility issue which resulted in their discontinued use of the Specialty Green coolant after just a couple of years, at which point they switched to the Motorcraft Orange which is thought to be similar to Dex-Cool, in mid-2011. My internet surfing suggests that the water pump failures have declined somewhat with the introduction of the new coolant beginning with model years 2012 and later, but they have not been completely eliminated on low mileage engines.
Bottom line, what should Ford owners with any of the 3.5L Duratec or Ecoboost engines do to avoid water pump failure and the related engine destruction.
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