Antifreeze leak at cylinder head. Do old heads become porous?

[Raymond R.]

I thought the leak was from the first bolt in the cylinder head. I took the bolt out. Cleaned it. Put on permatex and reinstalled. It now looks like the leak is from the casting below the bolt. The engine is a 327 ci, 250 hp. It doesn't look like there is a crack. It looks like the antifreeze is coming out of a pin hole. These are original heads. Do they become porous? If so, can they be fixed?

[Joe L.]

Re: Antifreeze leak at cylinder head. Do old heads become porous?

I thought the leak was from the first bolt in the cylinder head. I took the bolt out. Cleaned it. Put on permatex and reinstalled. It now looks like the leak is from the casting below the bolt. The engine is a 327 ci, 250 hp. It doesn't look like there is a crack. It looks like the antifreeze is coming out of a pin hole. These are original heads. Do they become porous? If so, can they be fixed?

Raymond------

They do not suffer casting porosity, per se, as a function of age and use. However, they can become cracked (even though the crack may be difficult or impossible to see with the naked eye) or they can suffer corrosion damage over time which can result in a leak. I've never seen a block or head casting rust-through, though.

You might try adding a HD sealer to your coolant to see if that solves the problem. You should be doing this anyway. Use GM #3634621.

[Raymond R.]

Re: Antifreeze leak at cylinder head. Do old heads become porous?

Thanks Joe. I will give the HD sealer a try before I start tearing it down.