Core plug replacement
 

Another stupid question :)

I'm replacing the core plug above the crankseal - now that I've opened it up, this was definitely the source of my leak!

The core plug goes in with the flat side facing into the engine block, right? I had always assumed it had gone the other way :shocked:

Also, does anyone know if I should be using a sealant when fitting the plug - and if so, what sealant?

Any other generic advice while doing this is appreciated - about to put everything back together

yes flat side in first , no sealant on a core plug it is a tight fit in the hole. find something round which fits in the core plug with a slight bit of play then be positive and hit it in firmly not small taps . use a larger hammer.

Pretty much as Clan has described. Make sure the surfaces on the block are clean before fitting the plug. Scotchbrite is great for cleaning up the surfaces. I normally use a long impact socket that fits inside the hollow of the plug. This allows you to hold the plug in place with enough length in the socket to safely strike it with a hammer. Try to keep the plug square when striking the socket.

Core plugs are an interference fit, so if both surfaces are clean and free from pitting, it should form a permanent seal once tapped into place. No need for sealant. You can in some cases go too deep with a core plug, so check the thickness of the material to see how deep you can afford to go with the plug. You ideally want to seat the core plug just beyond flush, ensuring that the full circumference of the plug is in even contact with the hole into which it is being fitted.