CBO

Update. Ended up replacing Oil Cooler Lines with OEM replacement. The plug is sealed by a tapered O-Ring. Original O-Ring was hard. Thanks for the help!

Hello Guys, First off, I would like to say thanks for the future help with this one! I own 2013 GMC Sierra 1500 SLE that I purchased New. It has been a great truck. I do all of my own maintenance on the truck. Engine is a 5.3 with 128k and counting. While doing an oil change I noticed some fresh oil residue / minimal drip on the bottom rear corner of the oil cooler line block off plate. After cleaning the block off plate I found out that the plug in the rear of the block off plate had a slight leak. Oil lines and all connections are good. Gasket isn't leaking. My question is, what is the reason for this plug? Mechanical oil gauge? I would like to remove this plug with a 3/8" Allen and reseal it with black Permatex. Any suggestions? I have searched the world wide internet for this exact issue and have struck out. Any help will be much appreciated. Thank you!