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Discussion Starter · #1 · (Edited)
So, I just completed oil cooler replacements in both of my trucks ('04 Excursion and '04 F250). The Excursion had blown its cooler which is what forced me into completing these jobs. After it was reassembled, everything was normal. Thermostat looked good. On my trip to work yesterday, Engine temps fluctuated between about 198* and 212* on my run to work, with some temps as high as 220* on the way home in 95+* heat and on the interstate in stop and go traffic then up to 70 mph. Oil temp never fluctuated more than 12* from the coolant temp. This job and system flush was a success...

The F250 on the other hand... When I pulled the thermostat, the o-ring stretched and I had to go buy an aftermarket replacement thermostat that came with the housing assembly. I had figured that my thermostat was bad anyway and opening too early, there were many days in the winter that the coolant would not warm up enough to make heat for the cabin. That said, now that it is back together, the coolant temp will not rise over 192*. I am monitoring with the SCT Livewire (in both trucks mind you) and the temps seem to mirror each other until the coolant temp reaches 192 and it stops and the oil temp keeps rising.

Now, if you assume that the coolant temps should mirror what I saw on the Excursion, then the oil temps are not much out of wack. Of course, I am thinking that this thermostat may be opening too early as well which could keep the coolant temps down and the oil temps slightly elevated... You think I have a bad temp sensor or to cool of a thermostat (supposed to be a 190*) or both....

Your thoughts...
 

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Opening point of the stock thermostat is 192 degrees. In my experience, unloaded, even with very high ambient temperatures its hard to get the temp over 194 if the truck's unloaded. Towing is a completely different story that depends on the grade, the load, etc.

What oil cooler did you use?
 

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Discussion Starter · #3 ·
Granted, it was an aftermarket cooler. I bought them long ago before I had read several threads about them not being very good, not sure what brand went into the F250. Now, I put a Dorman one in the Excursion and everything on it looks okay. However I am surprised at the coolant temp differential between the F250 and the Excursion.

I figured that since neither of these trucks have had coolant filters on them and the coolers went bad (one ruptured) that I would put in the cheaper aftermarket ones for now with plans to change them again in 6 months to a year with OEM, figuring that the newly installed coolant filters may not catch everything.

But the oil temps between both trucks is about the same. Funny how the oil temps between two trucks is really close, but the coolant temp varies. Would the Excursion really just run higher temps than the F250?
 

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I'd be a lot more worried about the Excursion. Not towing and reaching 220° F.? What's going to happen when you put a load on that thing? Did you flush the radiator? Might be gunked up with the residue from your blown cooler.
 

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Discussion Starter · #5 ·
I flushed many times with boiling water until nothing but clear water came out. When I said it reached 220*, that was like rolling off the interstate to a stop, it was not sustained an any way. ECT mostly below 204* as far as sustained driving with deltas no greater than 12*.

Is the Excursion really that much heavier than a F250? I still find it hard to believe that the Excursion will run 204* ECT and the F250 will not get above 192*. If the thermostat opens at 192, then it should vary between 192* and say 200* based on speed and acceleration, correct?

I am not arguing anyone's point, just trying to make sense of everything in my head so that I can take the proper steps to correct rather than chase something that is not a problem.
 

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The Excursion's weigh difference over the F250 is insignificant - probably has less wind resistance so going down the highway would be less work. You have no problem with the F250. I'm still a little worried about the Excursion. I'm not sure boiling water is the cure all for oil sludge. Might need a chemical boil out or at least a round of simple green run through it.
 

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Typically when they start to approach the t-stat opening temp you hit 192, then it stabilizes and if anything it will drop 2-4 degrees once it opens. Remember before it opens you are only circulating coolant through the bypass system. Once it opens you get full flow through the radiator, which at interstate speeds should offer a significant temperature differential.

I think I'd swap the temp senders between the X and the 250 and see if the results are the same.
 

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Discussion Starter · #9 ·
Sorry, forgot to mention I did run simple green through with boiling water, twice, then just boiling water until it ran out clear.
 
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