Good points @Trunk Monkey but I do think there are relevant counterpoints which keep sunlight on the table as a possible explanation for the OP's burns. Obviously we don't know at this point, but I still think sunlight is the leading explanation until more information is presented...
4ish days is an interesting clue.
I'd guess 5 days and that cloud cover or similar shade came in and interrupted the process on the 4th day, based on the burn lines. I'm guessing that each line is a different day and that the suns movement to the North caused each subsequent line to be added...
A few more questions:
was the sunroof's sunshade open?
seems like sunlight passing through the sunroof and then reflecting off of the rearview is another possible scenario similar to the drivers door mirror above.
is there any obvious shading of the parking location that would help narrow in...
If this damage is indeed from concentrated sunlight I imagine that reflection was involved and that reflection on one/more surfaces could explain the possibly inverse direction of the burns and sun's travel.
For instance if the sun were to hit the drivers rearview mirror later in the day then...
Looks like heat damage so concentrated sun light plus time may explain it. If this is sun damage then you should be able to figure out the direction the sun was moving and see variance in angle/strength over time. Perhaps there were focused dots that moved over time causing those stripes...
My thought on distilled vs tap is that it's really important for water left in the system for a long time but not that important for initial flushes. I'm basing this opinion in part on years of operating a raw water cooled gasoline engine in a sailboat operated in salt and brackish water. The...
There are scenarios where it will make sense to do what you have to do to make the truck reliable, or sell it, but if the rig was driveable I would definitely consider what 2001LC suggested. The biggest risk you would be taking it seems like would be burning the engine up leading to the cost of...