I came home and replaced the faulty oil pressure sending unit and after a quick leak check I went to fill the tank and get dinner. Came home and looked underneath the engine, and especially that bolt. Everything was dry. Why the bolt was loose I don’t know, but retorquing it to the proper ft/lbs appears to have done the trick. I will keep an eye on it though. If necessary, it will be a timing cover gasket amd water pump change in the future.