Coolant for Ford 3.5 Water Pump


Dec 21, 2006
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: 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: 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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Haven't heard of notable gasket issues unless you were to use orange (Dex-Cool, 2EHA) in a vehicle not designed for it. Someone correct me if I'm wrong, but I believe the Specialty Green was a P-HOAT similar to OEM coolants from asian makes. P-HOATs are not known for causing premature seal failure, but then I don't know the exact chemistry of the coolant. I think it's rather unlikely the use of specialty green or the yellow G05 coolant would contribute to seal failure. I am more inclined to believe that the water pump design was botched by Ford as this issue it not terribly uncommon in 3.5L engines. Lots of engines use a chain driven water pump, but it should be designed that the coolant *should* (except in isolated cases) exit the chain cover in the event of a leak or seal failure. I've heard too many reports of coolant in oil via bad water pumps in these engines to believe that it is just a fluke. When the water pump (also inside the timing cover) failed in my VG30 engine, it was evident through coolant leaking onto the ground through a channel built into the timing cover-- which the Ford should do if designed correctly. Personally, I would use the coolant Ford recommends in the chart, which appears to be special green in your case. There's nothing inherently wrong with SG that caused Ford to discontinue it, it was simply an attempt to move all platforms to a common coolant, which ended up being the orange. This likely involved some minor redesign or changing seals to make all engines compatible with orange (similar to Dexcool) coolant which does have a propensity to cause premature seal failures in applications not designed for it. I'd be curious to know the impetus for Ford changing to SG in the first place-- my guess is it was primarily a desire to use silicate free coolant, which has the potential to create deposits in the cooling system if neglected.
Just use what they recommend in case it happens again you can show the dealer you used the correct Coolant/AF .
Ford uses a 2 seal design in the 3.5L engine waterpump. Any coolant that leaks past seal 1 should exit a weep hole cast into the block and drip just behind the alternator. The second seal will leak into the oil sump after dripping down the front of engine. There have been reports of seal 1 leaks that did not produce evidence of weeping behind the alternator = weep hole plugged? I am planning to do the wp - proactively- in my 2009 Flex this spring, getting all the tools prepared. This Flex is at 198,000km right now, no leaks thus far! I have changed the coolant at 140,000km using the factory dark green stuff.
I have been using the Specialty Green fluid for the last 40k miles or so, but I think the water pump bearing may be going out again as I'm hearing the tell tale noises at startup with coincide with a failing pump and "stretched timing chain", hence my request for input on alternatives. I'm contemplating pulling off the timing cover to have a look and see what is going on. This car has about 150k miles on it and is out of warranty, although the remanufactured engine may still have some coverage. Regardless, I'd rather take steps to maintain the water pump seal as a top priority. Lastly, the dual seal referenced is not the seal that fails. The seal that fails is the one that seals the impeller drive shaft from the bearings on the engine side. The dual seal goes around the perimeter of the pump and seals it to the front of the engine. When the bearing seal fails, fluid escapes directly through the impeller drive shaft hole and dumps into the engine. The other water pump seals are not involved in this scenario. My thought is to address three potential issues: 1) chemical stability/reactivity of the seal itself, 2) increased lubricity of the coolant, 3) filter coolant to remove any abrasives. One idea I've been contemplating is to revert to G-05 coolant as it has been proven in many applications and has widely been acknowledged to be a top performing product. I've also read good things about BMW blue coolant. Also, any ideas as to what kinds of coolant system filter I could use? Something inexpensive but that would provide me with the ability to see if the filter is getting clogged?
Looks to me like the current specs for the 3.5L is the orange (dex-cool) stuff. Am I missing something? As such, wouldn't that be the go-to as the current replacement parts should be up to date?
buck91, that is an option, but I'm concerned that the Orange coolant may also have issues since Dex-Cool is universally despised (for good reason) and I'm also not convinced that Ford has it right this time either . . .
Originally Posted by abs
buck91, that is an option, but I'm concerned that the Orange coolant may also have issues since Dex-Cool is universally despised (for good reason) and I'm also not convinced that Ford has it right this time either . . .
Dex-Cool is a perfectly good coolant. Saying it's universally despised is ridiculous.
dogememe - Not trying to start a debate about dex-cool here, it's been debated enough. My impression is that Dex-Cool has had a range of famous issues, hence my statement. In a properly designed application, I'm sure it's fine.
If one can keep air from mixing in with Dex-Cool (with the OEM Ford degas bottle), and prevent morons from dumping in non-compatible coolant, Dex is a perfectly fine coolant (junk GM nylon LIM gaskets notwithstanding). There may be something to PHOAT/Specialty Green/Asian coolant damaging WP seals, there's been problems with some Toyota ones (1.8 1ZZ-FE for example) failing prematurely. Hard to believe Ford would duplicate the idiotic Chrysler 2.7 timing chain driven WP design, though-even for Ford that's a dumb move!
Originally Posted by abs
dogememe - Not trying to start a debate about dex-cool here, it's been debated enough. My impression is that Dex-Cool has had a range of famous issues, hence my statement. In a properly designed application, I'm sure it's fine.
The problem a few co workers and myself witnessed with dexcool was that hoses material was changed and having issues rotting from inside. We used/e it at my work without issues and correct coolant in other vehicle makes. SteveSRT8 i believe knows some about the dexcool "old wives tales" also
Get some Zerex G-05 or G40, both are Silicated OATs , which the all alu Ecoboost should like. And before somebody says it, no, Silicates do not wear water pumps or water pump seals.
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