Loss of coolant! I have a 2003 6.0 diesel with 200,000 miles. I put in a new oil cooler and ipr egr delete two years ago also flush the system and added a coolant filter. I filed it back up with the red antifreeze. Now the problem I have never lost any coolant since then and my deltas are about 5 degrees. But the other day I pulled a heavy load the first one since I did the repairs (coolant got up to 220 degrees and would drop back down) when I got home the coolant tank was about a inch low. I let the truck sit about 3 hours and checked it again and it was back at the full mark. Drove it the next day and it's back low about a inch does anyone have a clue what's going on. Also sorry for being long winded just trying to give all the info.

 

Mine does the same thing... you really didn't lose anything. I don't worry about the fluctuation from day to day, just the trending level. If its down today and continues to drop over time, I'd be a little concerned.

 

I've noticed the 6.0 has a mind of its own when it comes to coolant. I added some once and it spit it out at me so I just keep an eye on it.

 

I second that. I have mine pretty low in the bottle and after a good drive sometimes it will be past the top of the sticker when warm and sometimes it will be at the min line (new max) Heck after I did my delete and finally changed the degas bottle and cap (5th cap) it took me a month to get it where it wanted to be.