2013 GMC Sierra 5.3 Oil Cooler Block Off Plate Plug

CBO · March 17, 2021

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!

CamGTP · March 17, 2021

It may be a test port for oil pressure.

If it's leaking just remove it and put some thread tape on it and put it back in.

CBO · March 18, 2021

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!

Candace · November 7, 2023

I have a 13 Silverado and the exact same thing is happening. We replaced the oil cooler seal thinking it was that but it’s not. It’s the plug itself and when took out that tapered seal is hard as a rock. I’m having issues finding that seal or even that plug. Where did you find yours?