What is this and what is the purpose of this? The larger opening and the smaller one. Picture taken from the front of the cylinder head. I am pretty sure coolant leak, very small but it’s there. Having replaced the head gaskets not too long ago, this doesn’t make me feel good about it. Thanks.

 

Expansion(freeze out) plug.

 

Thanks. So should I be worried lol? Every couple of days there is a build up of fluid. I’m guessing this second engine has about 240k miles. Thanks for the info.

 

just watched a couple of videos. Makes sense now. I wished I’d know when the heads were out would be a lot easier to replace. But it’s doable.