Cylinder head 1-3 cracked near cylinder #1.
One day while driving home from work, the red light near the engine temp. indicator started blinking, but the temp. was normal.
The blinking indicator means that the coolant is low. Sure enough, when I checked the level, it was in fact slightly low, so I topped it up. However when I did so, i noticed a very small amount of oil in the coolant. This was concerning.
The next day, everything was seemingly fine, but after several miles the temp indicator light started blinking again! The temp. gauge was a little below normal, which was unusual, but far from hot.
Sadly, when I checked the coolant level this second time I found that my engine had decided to mix some very thick oil and coolant martinis -the reservoir was full of emulsified oil and coolant goo.