Coolant Temp Concern
About 4 weeks ago, my wife was driving my truck and explained that the Scanguage displayed ECT 202 & EOT 212, while some white smoke came from under the hood while at a stoplight. I had a friend come over and look the engine over, which he found no signs of "puking" from the degas tank or any other locations for coolant to expel from. The oil did not show any signs of contamination. The degas tank has always remained at the "minimum" mark while cold, about a 1/4" below the line actually. Normal temps: ECT 188-192 / EOT 194-198. This was on a day that was about 55 degrees. My friend checked the EGR Valve after it was brought to approx 175 degrees or so (i know, not full op temp). The truck was parked with the nose down in the driveway and he removed the EGR valve, which was dry and coated with dry soot (he cleaned and reinstalled). Maybe a 3/4 of a gal of Ford Gold and DI H2O was added. My wife drove it several more times and it did not repeat the issue of white smoke expelling from under the hood.
I looked over the truck on Dec 21 and still could not find any signs of leaking. The oil still looked and smelled as it should. The coolant was level was still right below the "MIN" mark when cold. i drove it and got the temp up to 190 for ECT with the EOT fluctuating between 4-8 degrees above. I did not WOT since I wanted to see how it was running. The next day I drove it to work (27 miles / 1/2 interstate 65-70mph) and the ECT/EOT were the same. The next morning, it was 48 and the ECT did not go above 187 with the same temp spread for the EOT 4-8 degrees above. The previous day it was 54 degrees.
I checked again around the engine and no apparent cooling loss and the degas tank level remained about the same. I have driven it a couple more times, to include work this morning and had it up to 70mph with the same temp indications.
I have not seen any white smoke when accelerating or idling after warmup. The only white smoke I have seen, is a slight puff when first cranked and cold.
The Mods I have are listed in my Sig... This is my 2nd 6.0l (first was new '04 and set up similar - sold '09). I purchased this one in Sep '11 with 131k and now has 150k.
Heavy Assault and I have chatted about potential issues, but now close to the holidays, thought I'd reach out with this new ECT/EOT temp difference. From what I've read, I'm thinking it may be a thermostat going out. The previous owner followed the maint sched and had the Gold changed at 100k (flush process/t-stat update/rad cap update - ????). NavyAd has also assisted in some ideas what may have caused the original occurrence.
My plan is to replace the T-stat and degas tank cap, to see if the ECT/EOT normal back and show a 190-192 ish range for the the t-stat to open. I need to replace the oil cooler, stud it, coolant filter, and leaning towards IPR Gen 2 EGR delete.
Appreciate any insight or feedback. The ORG has provided me an abundance of resourced information and community of fellow enthusiasts.