What are freeze plugs for?

[Ken4]

Also known as core plugs or soft plugs. Can anyone tell me what they're for? They are a nuisance for me as they eventually corrode and leak.

 

[sub_zero]

They protect the engine block incase the coolant freezes inside. The subsequent expansion of the freezing water into ice will dislodge the plug allowing the block to accomodate. Otherwise you will have a cracked block.

 

[TooManyWheels]

The freeze plugs are where the inner mold (for the water jacket) and the outer mold of the block casting were connected when the block was cast. They also provide an avenue of expansion for freezing water which has not been treated with antifreeze.

 

[Ken4]

My MB280S has bolted-on plate type of freeze plugs. I dont see how it can dislodge itself or break if coolant freezes.

 

[JohnnyO]

quote:

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Originally posted by Ken4:
My MB280S has bolted-on plate type of freeze plugs. I dont see how it can dislodge itself or break if coolant freezes.

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Correct, it won't. Guys who build hi-perf and race engines often put in screw-in plugs because they're stronger. MB either assumes you'll keep proper coolant in or maybe they have another way for it.

 

[got boost?]

does anyone know for sure that they are intended to provide expansion room for freezing coolant? I've seen too many blocks crack before the freeze plugs budge to believe that. I think TooManyWheels is correct.

 

[Ned Nimrod]

Core plugs are used to plug the hole where the core sand is shaken out. The engine blocks are picked up by a device that shakes the sand out of the holes. It is part of the casting process.

 

[Kestas]

Ned has it right. I used to design and qualify automotive castings for Chrysler. The primary function of these holes is for shakeout of core sand at the foundry. I seriously believe the term "freeze plugs" was the result of somebody trying to put a positive marketing spin on this feature. I don't think these holes would protect the block from cracking during freeze-up.

 

[tom slick]

i also agree with ned. it is for dumping the sand out. water expands evenly, so a few small plugs placed in the middle of the outside of the engine block isn't going to give you much protection from "expanding ice water".

 

[Gary Allan]

quote:

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I used to design and qualify automotive castings for Chrysler.

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I don't suppose that you're to blame for the lousy block castings that plagued Chrysler in the 70's???? Sand core shift seemed to be a problem for them in their V8s.


Anyway ...yes, sand core removal ports. As was mentioned castings are placed on a shaker table ...the sand finds a way out through the holes.

[ January 11, 2004, 02:40 PM: Message edited by: Gary Allan ]

 

[Kestas]

I am not shocked to hear that. I am also glad to say I started there in 81, though I humbly won't take ALL the credit for improvement since then.

If the plants would only build cars the way engineers specified them on the print, we wouldn't have anywhere near the problems we see with cars today.