What is this on "feeze plug?"

tank1949

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I have never seen a brass freeze plug with, what appears to be, an aluminum wafer glued or pressed on to it. I have included photo, but flash has bleached out the aluminum (size of a nickel) part. Motors are anti-freeze cooled, so saltwater should never be able to eat out. These are V8 Chevy motors. Does anyone have any idea what or why plug manufacture would add this aluminum to their brass plugs? THX!
 

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QBhoy

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Not sure if I’m thinking too simply, but this is just what they are. Thin bursting disc is going to be just that for it to work, should it need to.
 

tank1949

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Not sure if I’m thinking too simply, but this is just what they are. Thin bursting disc is going to be just that for it to work, should it need to.

No disrespect, but that makes no fnnn sense, since freeze plugs were not originally designed for relieving blocks in case the inside fluid freezes but help in the casting process. However, if the brass is pushed out by freezing water, to me the bursting part is redundant? I am still scratching my head.
 

Bt Doctur

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The aluminum disc is a overheat indicator installed by the manufacturer. Should you need to make a claim and its not there you severly overheated and lost any warranty
 

tank1949

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The aluminum disc is a overheat indicator installed by the manufacturer. Should you need to make a claim and its not there you severly overheated and lost any warranty

What is it supposed to do? I assume fall off if a certain temperature is reached??? Define overheating, > 220 degrees??? I have never seen one of these but your logic makes sense.
 

Big Gee

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I've heard them called heat tabs. Here's an excerpt from this:
http://www.sbintl.com/tech_library/articles/keeping_tabs_on_engine_temperature.pdf

"A typical heat tab for a gasoline engine has a center plug that melts out at 250º to 255º F. If the engine has gotten hot enough to melt the heat tab, any damage it suffered is likely not the rebuilder’s fault. Lower temperature heat tabs are also available for other applications such as marine (187º to 192º F) and diesel (225º to 230º F)."
 

tank1949

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Are you able to see a label on yours? As the following site suggests some may have wordings and/or be color organized for engine designation to engine temperature matches...,https://www.engineheattabs.com/products

yeah I can but I will need bright light and better pair of eyes to see details. I am old! I believe both motors have them, which indicate "crate" motors. I have used a local machine/motor shop to purchase their reman marine V8s and automotive engines, and they have never added one of these to their freeze plugs. The last engine I bought from them was about 4 years ago and none of these tabs were installed. THX!
 

Scott Danforth

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Common heat tab. All my machine shops use them on engines the assemble.
 

Lou C

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The re-man cyl heads I installed on my 4.3 a couple of years ago have heat tabs on them.....
 

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