Check the hoses and take a second look at the fittings.
On mine, the upper radiator hose was leaking for a while before I found it (even the two Indy's I went to didn't find that leak). The fitting was rotting out and was discolored. It was only after I took it off that I was able to determine that was the source.
That hose has a small nipple for a y hose that runs under the intake manifold, which crumbled as soon as I tried to remove it. There was never any obvious signs of a coolant leak except the low coolant warning (once) and once or twice the smell. (1 and 5 in the image)
Bought both hoses and no more leak, at least til the valley pan leaked later.
I went ahead and replaced the reservoir cap too. All cheap, easy and time friendly fixes along with little more peace of mind that I wasn't going to be driving down the road and see steam billowing from under the hood without (much) warning.