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What I have to figure is happening is, in high gear, at low rpm and high boost, the turbos are generating a TON of heat. The turbos are water cooled, and oil lubricated. A massive amount of heat is being passed to the engine coolant. At low rpm, the fan is not pulling as much air, and that really superhot coolant is cycling thru the engine and radiator without losing much heat. I think that's the problem more than increased IATs.
If I remember correctly, coolant flow (for sure for 2.7's, probably also for 3.5's) goes rad > turbo > head > block > rad.
This is supposed to help the block (and oil) warm up quicker, but a really hot turbo on a hot engine will really warm up the block, more than the cooling system can handle.
As mentioned, air flow and higher RPM's will solve mild overheating, drop a gear and keep moving, but slow down. There is a tipping point where you just can't recover and get temps down, and if lower your speed and running higher RPM isn't helping, then you've got another problem on your hands that needs to be addressed.
What I have to figure is happening is, in high gear, at low rpm and high boost, the turbos are generating a TON of heat. The turbos are water cooled, and oil lubricated. A massive amount of heat is being passed to the engine coolant. At low rpm, the fan is not pulling as much air, and that really superhot coolant is cycling thru the engine and radiator without losing much heat. I think that's the problem more than increased IATs.
If you stay in boost up a long grade, you will overheat. Cooling the charge air helps because it lowers IAT2, which is pumping through the motor. I have the upgraded Full Race radiator, and I can say when I drop down and increase RPMs (More coolant flow) the motor cools off, regardless of what the fans or airflow is at the radiator. To me this says that the upgraded radiator has no problem shedding the extra heat, but cannot do so if the turbos are increasingly dumping a huge amount of heat. IMO it's the turbo heat soak that causes the overheat.
Regarding the flow of coolant - On the 2011-2014s (not sure about 2015+) here is the flow diagram. It looks like the flow is Rad>Block>Then splits to Head and Turbo >Rad. So the turbo is pretty much at the end of the cooling line. Not only that, but the cooling lines are pretty small. If the motor is already hot from pulling a grade, imagine having a hot turbo on top of that --> overheat.
If you stay in boost up a long grade, you will overheat. Cooling the charge air helps because it lowers IAT2, which is pumping through the motor. I have the upgraded Full Race radiator, and I can say when I drop down and increase RPMs (More coolant flow) the motor cools off, regardless of what the fans or airflow is at the radiator. To me this says that the upgraded radiator has no problem shedding the extra heat, but cannot do so if the turbos are increasingly dumping a huge amount of heat. IMO it's the turbo heat soak that causes the overheat.
Regarding the flow of coolant - On the 2011-2014s (not sure about 2015+) here is the flow diagram. It looks like the flow is Rad>Block>Then splits to Head and Turbo >Rad. So the turbo is pretty much at the end of the cooling line. Not only that, but the cooling lines are pretty small. If the motor is already hot from pulling a grade, imagine having a hot turbo on top of that --> overheat.
With the 2015's they reversed the flow of coolant, and the block gets it last now. This is at least 100% for the 2.7 Ecoboost, but I'm unsure if they also changed the 3.5L to do the same.
Interesting. There are a lot less reports of 2015+ trucks overheating, so I wonder if this is the case for the 3.5L. It would make more sense this way because those turbos get smokin hot.
With the 2015's they reversed the flow of coolant, and the block gets it last now. This is at least 100% for the 2.7 Ecoboost, but I'm unsure if they also changed the 3.5L to do the same.
Based on the parts diagrams, the 2015 3.5 has the same waterpump and thermostat housings as the 2014 so I would say they are still the same through 2016.
I was reseaching this too! lol. Funny how everyone reads both forums! It appears the difference is Gen 1 vs. Gen 2. The inlet definitely looks different. The thermostat rests in the manifold crossover tube. I wonder if this would fit the same timing chain cover? The part numbers are different, but I can't imagine they changed the block. Perhaps the cover is just different as well?
Based on the parts diagrams, the 2015 3.5 has the same waterpump and thermostat housings as the 2014 so I would say they are still the same through 2016.
After further reading, it seems the 3.5 EB prior to 2015 already had the reverse-flow cooling, and the 2.7 just followed suit. So the ecoboosts have already been like that it seems.
