freeze plug??
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Joined: Nov 2004
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From: N. Mississippi
Freeze plugs are supposed to "pop" out of the block if the coolant freezes in the block. They are left over from the block casting process so plugs are put in to seal them off. They work because I had a brother-in-law that had pure water in a Buick once and it froze and pushed 2 freeze plugs out.
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As I understand it the only designed purpose of a 'freeze plug' is to allow the removal of the casting sand after the block casting process. If any blocks have been saved by the plugs popping out it's probably a coincidence. Because if the water on the outside edge expands enough to pop a plug, the water on the other side of the block (I'm thinking exhaust manifold side vs intake manifold side on a bank of a V8) will expand just as much. Since there are no plugs on that side then the block will crack.
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Joined: Nov 2004
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From: N. Mississippi
Originally Posted by 76supercab2
As I understand it the only designed purpose of a 'freeze plug' is to allow the removal of the casting sand after the block casting process. If any blocks have been saved by the plugs popping out it's probably a coincidence. Because if the water on the outside edge expands enough to pop a plug, the water on the other side of the block (I'm thinking exhaust manifold side vs intake manifold side on a bank of a V8) will expand just as much. Since there are no plugs on that side then the block will crack.
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I don't know why they call them freeze plugs, unless it's because someone noticed they poped out when his coolant froze up.
Here's another good example. Most people in the snow belt will either cover or bring their bird baths inside because if the water in the bath freezes it can crack the basin. But the basin is completely open across the entire top. How can the water crack the basin if it is not contained and has room to expand up? Probably because as water freezes it expands at the same rate in all directions. The horizontal direction is contained by the basin and the pressure from the ice cracks the basin. Same thing in the block. As the water over the plug expands, it pushes the plug out but right next to the plug is water contained by the side of the block and as the water freezes (becomes more solid?) it expands and the ice in the plug hole blocks any further pressure relief.
Maybe under light freezing conditions the plug could get pushed out and the coolant still drain before it freezes solid in the block. But I've never been that lucky in those kinds of things. Further, if that did happen, how long would it take for the average non-mechanically adept driver to notice that his engine is burning up due to no coolant?
Here's another good example. Most people in the snow belt will either cover or bring their bird baths inside because if the water in the bath freezes it can crack the basin. But the basin is completely open across the entire top. How can the water crack the basin if it is not contained and has room to expand up? Probably because as water freezes it expands at the same rate in all directions. The horizontal direction is contained by the basin and the pressure from the ice cracks the basin. Same thing in the block. As the water over the plug expands, it pushes the plug out but right next to the plug is water contained by the side of the block and as the water freezes (becomes more solid?) it expands and the ice in the plug hole blocks any further pressure relief.
Maybe under light freezing conditions the plug could get pushed out and the coolant still drain before it freezes solid in the block. But I've never been that lucky in those kinds of things. Further, if that did happen, how long would it take for the average non-mechanically adept driver to notice that his engine is burning up due to no coolant?
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Joined: Feb 2004
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From: Marengo, Iowa
they are just for getting the sand out, somewhere along the line, someone got the idea that they will protect the block, but I can guarantee that the block will still break with those soft plugs in them, I have seen a side split out when they left straight water in over the winter, and had soft plugs right in the middle of the section that broke.
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Joined: Nov 2004
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From: north west new jersey
Originally Posted by fellro86
they are just for getting the sand out, somewhere along the line, someone got the idea that they will protect the block, but I can guarantee that the block will still break with those soft plugs in them, I have seen a side split out when they left straight water in over the winter, and had soft plugs right in the middle of the section that broke.
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Joined: May 2004
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From: The hills of No. Calif.
If you notice that fellro refered to them as "soft plugs", that's the more common name for them these days probably to try to get away from the old misconception that they will protect your block in case of a freeze. Antifreeze/coolant does a bit better job! I have als heard them refered to as core plugs. -TD