[Nebster]

Okay, fingers crossed indeed. Sounds like there are a lot of fairly benign reasons this could be happening. I don't have any documentation to know whether the coolant was recently flushed, but it's certainly possible. The radiator cap itself seems broken to me (retaining tab bent such that I needed pliers to remove the cap one time), so it could easily be the culprit. I have to go to CAT for a variety of other things, but this is my top priority. Will report back soon. Thank you!