yup!
You got it right. Oil cooler. I just found it on a service manual I found online.
Thanks so much for those who do this for all of us. I have a copy at home, but not here. Thankfully the guys at TTORA had some online.
Here's a picture:
Now would the o-ring be at fault, or the cooler itself is the question?
The motor shown is not mine. It was just a clear picture I found while looking for somebody with the same issue as me. Many people apparently have the coolant lines above the engine crack and leak into the manifold space. This is not leaking from there, and it's pretty clear it's not leaking from the head gasket either. I guess an internal leak could pressure the system causing it to leak when engine running, but it leaks when not running as well.
I'm going to go rent a cooling pressure test tool today if possible and do the tests. Seems easy enough especially if I don't have to buy the tool! Then I can narrow down what parts it might be.
Thanks for the helps guys! I'm hoping it's as simple as replacing that 0-ring. I wish it was warmer than -25 though! Brr