Leon Speed

Is replacing freeze plugs a WYAIT or are these left alone when they donīt leak?

Why does one side of a head have a freeze plug and the other side a threaded plug (core plug)?

Randy V

Unless I'm mistaken, those freeze plugs should last the life of the engine.

If yours are corroded/leaking it indicates significant internal corrosion of the water passages due to infrequent coolant flushes.

Eplebnista

Given the location of the plugs pictured here, I would agree that they should last the life of the engine because of where they live. Otherwise, I disagree with the statement that freeze plugs should last the life of an engine or the implication that any corrosion related leak is due to poor cooling system maintenance. While I have never replaced a freeze plug on a 928, I have done some others. They all rotted from the outside in. In fact, unless I finally threw it out, there should be a GM freeze plug rattling around the back of my VW wagon that is pristine on the engine side and rotted through on the outside.

Randy V

https://rennlist.com/forums/8588060-post16.html

Leon Speed

Ok thanks for the insight guys. Thanks for the link Randy, provides some good info. The problem is, I don't know if it rusts from the inside or outside. The rust appears to me as surface rust, but there are white deposits there as well. Then there are white deposits/oxidation spots on the upper parts of the heads, but that can't be from coolant. I've had this car for four years and in all those years the coolant stayed at the same level in the tank. I can't make sense of it...but I need to inspect the rear plugs.

Eplebnista

Ok, I have learned more about 928's and the doubtful wisdom of applying general experience to these cars. I have zero experience with aluminum blocks that had the same coolant in them for long periods of time. I defer to the superior 928 knowledge of others and stand corrected.

Now that I have admitted that I know nothing, I will offer my view on the original question. I would not regard replacing freeze plugs as a WYAIT. If the rust really is surface rust, clean it up and shoot a little paint on it or just leave it be. Replacing freeze plugs is generally a WYAIT when you have already pulled the engine out.