cyl head freeze plug
 

I'm in the process of trying to repair every little oil leak I can find on my 99 before it's reassembled, and I noticed that there is oil collecting on the lower half of the freeze plug on the side of the cylinder head. (small plug, size of a quarter)

This may be a stupid question, but if this plug were to be leaking, there should be coolant dripping out of it and not motor oil right? I'm not sure if this was used in casting and covers an oil gallery or not?

Any takers?

I never noticed that little plug before.

The pressurized oil feed from the block into the head comes up right between #2 and #3 on the intake side. Here's a picture looking down onto the deck surface of the block with the head removed. The feed in question is circled in red:

https://www.miataturbo.net/attachmen...ine=1322535519

Not exactly rock-solid evidence, but it certainly seems plausible that your mystery plug is on the main oil galley.

Hmm subbed for answer ... I will tell you that if you choose to replace it this plug is not included in the rock auto brass freeze plug set, I'm doing the same sort of build and am very glad I didn't pop this out before I had them in my hand.

r r r r ra ra rarrr RTV THAT BITCH

Well, I ordered one online and after removing the old one, it most definitely is a water jacket plug. No biggie, the oil must have been from the valve cover which was also leaking like a sob.

So now you know, and knowing cost me about tree fiddy. :giggle: