Tech Area

Freeze Plug

Question: What and where are freeze plugs?

Answer: A freeze "plug" actually fills a hole in the block/heads water jacket that was designed to hold the block/head during the casting process.

But, by having a softer plug fill the hole after casting is completed, the theory is that it (the plug) will push out before the block/head cracks if coolant/water freezes within the castings. Over time, the plug can erode, pinholes develop, and coolant will escape, especially under pressure.

There are 3 freeze plugs on the starter side of a 4 cyl block (if I remember correctly). One is just above/behind the starter. Usually fairly simple to pry out after the area is cleared, but a bit difficult to drive another in. There are rubber "expansion type" plugs, but they need to be checked carefully to make sure they do not try to slide out of the hole and cause a massive leak. Engine will not have to be removed.

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