Increasing RPMs cools the engine

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skamerick

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After researching possible solutions to the overheating problem with my 2017 EL , I found several posts (mostly from F150 owners) that had some very interesting suggestions. I'll admit up front, this is my first experience with a turbo changed engine, so I found their suggestions a bit strange. As I began a steady climb, my temp gage would start climbing also. My first response was to slow down, which also reduced the RPMs. Then I read that my response should have been to shift out of Drive and into Manual, then dropping to a lower gear (6 -5 - 4 - 3) as necessary to maintain my speed, but increase the RPMs. To my absolute amazement, I watched as the temp gauge returned to normal. I always thought that increasing an engine's RPMs would make the engine work harder, thus increasing the engine temp.
I would never have believed anything different, until I saw it with my own eyes.
Someone (please) with a better understand of my Expedition's engine, help this own guy understand how this works.
 

JasonH

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Lower gears use leverage to reduce the load on the engine. Even though the engine is spinning faster, it's not doing as much work. Note the position of the throttle when you downshift...you can reduce the amount of throttle without the vehicle slowing down. The Expedition likes to increase boost instead of using manual leverage when towing. This results in a hotter intake charge and more heat generated in the engine because compressing air heats it up (Boyles law). By downshifting the engine sees less load, and thus less boost is needed because the engine is not working as hard.
 

LokiWolf

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Jason nailed it! Less Boost, less heat. Also, additional speed(Not fast) puts more air across the radiator, so more cooling.
 

caseyp

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Hey everyone, this thread nailed my problem and its solution. However, my question would be as to why this started happening to me recently? I have 2017 XLT 4WD, with 124,000. We used to drive up to the mountains of AZ all the time and this was never an issue. We pulled a trailer up there before with no issues. To provide a little background....I had a pinhole leak last winter and eventually realized water pump needed replaced. Could this have caused other issues?

This last trip the first major hills with grade we hit we overheated. Nursed it the rest of the way there and the trip home I used this method to keep temps down.

After 4 hours in teh shop, they couldn't reproduce the issue and that was a big fun bill to pay. Did have transmission oil changed out as it got cooked with the overheating. My biggest question is why this is happening now and used to be no issue. Thanks for an insight!
 

JasonH

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Could any number of issues. Stuck thermostat, cooling system obstruction, coolant mixture, gas in coolant, headwind, head gasket leak, poor combustion efficiency, bad fuel. Start with low hanging fruit like thermostat, hoses, fluids, and plugs. Then you can progress to compression and head gasket tests. Did any vanes break off the pump and get into the cooling system? Was all the gas released from the cooling system?
 

Timo2824

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A known issue with the water pump impellers failing, with your milage its probably worth checking.
 

caseyp

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for clarification, water pump was replaced in January. The shop supposedly checked cooling system, I imagine it would have tested thermostat, hoses, fluids, and plugs trying to recreate the condition, like you mentioned the low hanging fruit.
 
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