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Discussion Starter #1
I recently pruchased a bone stock 08 CC DRW 4wd manual trans, absolutely love it. Here's the problem....my temp gauge has stayed just a hair to the left of dead center straight up while driving since I got it about 2,500 miles ago, runs great no problems. Today I put a 15k tractor on my trailer and headed down the road, pulled it no problem, easily I thought. Then it started pegging the coolant temp gauge out about every 5-10 miles. It would go from normal to pegged instantly and the reduced power would come on. I pulled over checked the fluids and every thing was full and dry. The gauge would go back to normal and few miles down the road it would go from normal to pegged again, instantly. Got rid of the tractor and didn't do it again all the way home. Any ideas? thermostat? I'm new to the 6.4s and was really loving it until tonight.
 

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Bad thermostats perhaps? You don't hear of many overheating issues with the 6.4 since it moves a huge amount of coolant and has a large radiator.
 

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My money would be on the sensor for the gauge. Did the fan come on?
 

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Discussion Starter #4
The fan was running, but I figured it might since I was pulling a trailer, and especially if it thought is was in a overheat or hot situation. It was just strange how it went from normal to pegged instantly but went back to normal gradually.
 

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My money would be on the sensor for the gauge. Did the fan come on?
The symptoms sound to me more like it really was overheating, not a flaky sensor since the issue disappeared once he was no longer towing. It sounds to me like something is preventing proper coolant circulation and since we know there have been issues with the thermostats, that would be my first suspect to investigate.
 

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Discussion Starter #6
That's kinda what I was leaning toward, but the instant jump in temp was throwing me off. I haven't really looked at it much, how hard are they to get to?
 

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The instant spike makes me think some sort of thermostat issue preventing coolant flow and then it clears and the overheated coolant hits the sensor and spikes it, followed by a gradual cooling to normal temp and the issue repeating. The docs mention airlock issues, but I'd think that wouldn't consistently repeat.

http://wpnet.us/64_cooling.pdf
 

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Discussion Starter #8
I agree completely, thanks.
 

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Discussion Starter #10
Everything was full and dry, first thing I checked.
 

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Discussion Starter #11
OK, so I put a tractor on the trailer again today after changing the thermostats...same thing happened. Driving along just fine then the gauge pegged and the light came on. This time I had my temp gun and pulled over real fast...top hose was 175, bottle was 155 and the bottom hose was 95, gauge had come off pegged but was still near the red at this time. Got to be the ECT, right?
 

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Still leaning toward the sensor
 

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Discussion Starter #13
Changed the ECT, has new stats, still spikes the gauge and reduces power..only when working it and pulling a loaded trailer. Coolant temp never got above 203 as indicated by a scan tool.
 

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Discussion Starter #14
Ok, here is what I found out...The oil cooler is plugged up. Got a scanner that would read oil and water temp, water temp is perfect but oil is way high. Now the most important thing. My truck had the original ecm program in it which did nothing for high oil temp other than spike the gauge,turn the tempo light on and reduce power, no codes either. Got the ecm re-flashed, and them it started throwing the wrench light and set a code P012F. The reason I feel this is pretty crucial is that with that original program your oil could be boiling and you would have no warning, no code...nothing.
 

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Glad you found the problem, I don't recall reading about 6.4 oil coolers plugging up before. I do recall mention of that on the 6.0 but I've never had one of those.

The new firmware is important to get, particularly while you are under warranty since it can identify things for repair before the warranty runs out. I also really like the ScangaugeII for keeping an eye on the real coolant, oil, trans and DPF temps.
 

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Discussion Starter #17
The tech at the dealer I talked to is really good on the diesels, that's all he does. He said he has never had to do a cooler on a 6.4 yet. I googled my problem and saw several threads with the gauge spiking but no one knew why and it seemed like a lot of guessing. Hopefully this may eliminate some guessing for someone else.
 
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