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Random Overheating - NOT blown headgasket
Let me start by saying that I am a first time poster, but this forum has been helping me diagnose and fix issues on my truck for some time now just by searching old threads. I have searched all the threads I could read on overheating and tried appling it to my truck and still havent found a solution. My truck is a 07' F250 with the 6.0L powerstroke with EGR Delete, new oil cooler, new fan clutch, new water pump, new thermostat, new radiator, coolant filter, and Rotella Ultra ELC Coolant after recent flush with Restore/Restore+ and VC9. The problem is that the truck will randomly overheat while driving down the interstate and does it more often when the cruise control is set. As soon as it overheats I turn the heater on high and pull over, but there is never any heat while overheating. As soon as the heat stats blowing again the coolant temp drops like a rock. It almost seems like the thermostat is getting stuck, then when it unsticks everything is fine again, this is why I have changed the thermostat (only use OEM motorcraft parts) 3 times now thinking I had a bad/deffective thermostat. My EOT (measured on edge insight) usually runs 196-202 and ECT 192-196 when running down the interstate. When the problem occurs the ECT will slowly start creeping up and pass the EOT and get up to 230ish. Then suddenly the ECT will drop down to 184ish quickly and after that both EOT and ECT will level back out to normal running temps. It doesnt do this often, but it does randomly happen a few times per week. It doesnt happen around town only on highway, and doesnt seem to happen more or less when I am towing. By the way, I have done the self test with the kit you rent from the auto parts store for combustion gasses in coolant and show no signs of hg issues, and also took truck to local truck dealer who did a hg test and said there was nothing wrong with my truck. Any thoughts are greatly appreciated!!!
Last edited by cemerson12; 03-13-2012 at 05:31 PM.