Quazen > Recreation > Autos

How to Change a Freeze Plug

Here is a "how to" for the shade tree mechanic, and maybe even the pro mechanic.

It’s been a while since I have written anything, as I have had lightning strike my computer, modem, and router, which put me down for awhile. (Why do people want to move to Florida again?). I am very grateful and fortunate to be blessed with abilities in music and science (machines). The two do have a co- relation.

For example: I have long slender fingers with the coordination to play the piano, but this also comes in handy when I am working on engines. You may be able to relate to this, especially when you get to a nut or bolt that you just can’t get to!

Let’s face it. Some of the vehicles today are insane to work on. Either you have to be a contortionist and triple jointed, or have all of those “special tools” with some wacky number like 2a4487b24. Or a left hand threaded tap wrench with some ridiculous size like 6.5mm. I am sharing this in hopes that it may benefit the “do it yourselfer” or “shade tree mechanic.” For that matter, maybe this would interest a pro mechanic. Then, of course, I may not be the only one who has tried what follows.

I am first going to assume that whoever is reading this has some basic mechanical knowledge. I wish to shed a little light on the “freeze plug.’’ I have rebuilt and/or helped rebuild quite a few engines in my time, and have (like many before me) become familiar with the freeze plug. For those of us not familiar; a freeze plug is usually a round, dish shaped piece of metal, which is pressed or driven into the engine block and the engine head. There are multiple sizes, and usually multiple locations depending on the engine, and its maker.

A COMMON MYTH ABOUT THE FREEZE PLUG:

It is an expansion device made to prevent damage to the engine in case the water in the engine should freeze. The plug pops out, instead of the engine freezing.

FACT(s) ABOUT THE FREEZE PLUG:

Although it does function that way, in many cases the freeze plug is there to simply plug a hole. When a block or head is cast, there sometimes must be holes bored in various places, and filled with sand to prevent casting a big hunk of metal from being formed. The sand allows for things like water jackets and other “chambers” within the engine such as places for oil to travel and so on. It just works out that the freeze plug has dual “functionality.”

Unfortunately, after an engine is fully assembled, it is quite often difficult or impossible for repair to be made when a freeze plug fails, without removing the engine and/or transmission. Commonly, freeze plugs are located in the back of a head or block (sometimes between the transmission and engine). They may also be found on the sides of an engine, under an exhaust or intake manifold, creating a very costly and labor intensive repair.

Although the actual freeze plug may only cost around $3 to $10, the time it takes to replace it may take up to 8 hours. Luckily, there are different types of freeze plugs available, depending on your situation.

I discovered a freeze plug problem in my 1993 Ford F-150 when it was running hot, and would not hold water. I had a hard time trying to see where the leak was coming from, but I found it to be rusted freeze plug behind the engine block! I thought for certain that I was going to have to take the truck to a shop to have it fixed, and at a price of $300 dollars or more! (All for a $6 part). I kept thinking that the engine was going to have to come out, and that would lead to more problems because the truck is old- and there were a lot of rusty and maybe frozen bolts.

After carefully looking things over, I decided that if I could see the plug, I could get it out and replace it with a new one. The “operation was a success, and here’s how I did it: First, I drained the water out of the radiator. Then I turned the wheel of the truck hard left. At this point I cut out the plastic cover under the fender well.

Then I positioned a mirror on the bell housing of the transmission, facing the engine block so that I could see the freeze plug to be removed. I was able to get a flat blade screwdriver into the hole (the freeze plug rusted through) of the plug and pry it out. Then, I cleaned out the “socket” where the new freeze plug would be installed. This was done with a rag and a wire brush.

The new freeze plug was a two piece brass plug with a nut on one side. I simply pressed it into place, gently tapped it to insure it was in all the way, and tightened the nut. This expands the two pieces to fit tightly into the block. Below is the new plug.

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Comments (4)
#1 by keyboardologist, Nov 12, 2007
I had pictures to go with this article, but Triond removed them for some reason. I guess I'll put them on Picable, or try again.
#2 by jak3, Jan 3, 2008
clever way to access a difficult fix.

where did you get this type of brass plug ?

I need to do the same repair.

thanks
#3 by keyboardologist (writer), Jan 3, 2008
jak3, there are several different types of plugs available. there is a rubber expansion type (similar to a plug in a motorboat). And the brass/copper alloy type. The plug I used is copper. I found this at a NAPA auto parts store. These are fairly common, but you need to make sure the person behind the counter knows what they are doing. The "expansion type" freeze plugs have a precise fit. Carefully install this type of plug, as it is soft metal, and easy to break if you overtighten.
Thanks for reading this article, I hope it helps.
#4 by Austin Schnelting, Oct 27, 2008
I got told that if you hit on side of the freeze plug with a screw driver and and a hammer that it would turn then you could twist it out
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