Last year in December I tore into my '05 to do the semi-bulletproofing. I did oil cooler, BPD EGR cooler, STC connector, etc. No head gaskets at that time. Truck has been flawless since then. Coolant was flushed about 10,000 miles ago (before the oil cooler swap). I usually run Matt's 8k Tow tune as a daily driver unless I'm towing heavy.
In the past week I've used the truck a lot from towing a light box trailer 300 miles, running all around locally more than usual, & pulling a 15,500 lb fifth wheel a short, but hilly distance. Today I was about to do an oil change and I lifted the hood to see the degas bottle full and dark-ish.
The degas bottle level has been between the lines all year in all conditions, so clearly something is wrong. The color is a dark yellow, not the light yellow color that the coolant normally is. (Yes, I have Ford Gold in there; lets not get into all that debate in this thread) With a light or the sun on the degas bottle, I can still see light through t very well. All that leads me to believe that whatever happened happened this week so it's not been an ongoing issue and I probably caught it in time. My oil level is always at the top of the OK zone on the dipstick but today I checked it and it's a little bit down (maybe 2 X's down)
I've ordered a coolant test kit from amsoilAMSOIL - Oil Analysis Kits
to try to narrow it down. I truly believe that it's an oil cooler issue. and with a coolant flush and new oil cooler I'll probably be OK.
Anyone see any flaws in my logic or path here?
I'll keep this thread up to date so others can use it in the future.