Freeze Plug Corrosion Question

[Offbottom]

Hello Fellow Country Fellers:

Interested in hearing what you would do.

Changing the clutch in my 1959 Ford 841. I took off the large flat plate (about 1/8” thick) between the front and back halves. In doing so, I discovered the lower freeze plug on the back of the engine was filled with dirt and grime up to the top of the plate (the plate covers the bottom half of the freeze plug).

Okay, that needs cleaning. We leave nothing unclean when the opportunity exists to make things a little better.

Once clean, I further discovered about 3 pits in the lower half of the freeze plug. As you all know, there is nothing more effective in creating corrosion than dirt holding moisture next to steel. Turns out there is a good reason for keeping things clean.

I would estimate the pits are about 1/8” long/wide. I did not try to measure the depth of the pits. But just eyeballing, if the thickness of the middle of the freeze plug is the same as the visible edges of the freeze plug, one of them is probably pretty close to being corroded all the way thru the plug.

Well darn. What to do about this?

If it finally rusts all the way through, I’m back to splitting the tractor and all the joy that entails.

Would you?

• Fill the freeze plug hole with heavy grease and hope it doesn’t rust any deeper
• JB Weld the pits and hope for the best
• Remove the freeze plug and replace
• Try to spot weld the pits
• Do nothing, it already lasted 67 years
• Another idea, probably better than those above

If you said c.), how much trouble is removing the freeze plug and replacing it? That’s one I have never attempted before on any vehicle, just no need. I could use the tips.

So looking for a little advice and opinion on the topic.

This is unrelated but I might mention it here. I have only made two YouTube videos in my life, the first of which was my middle son playing HS football. The second one was about a week ago. All three of my kids are now grown and scattered around the US, so I thought I’d show them what I was up to with the tractor just for fun. It’s not a technical video that you will learn anything from; it’s just for my kids, two of which are engineers. I also give a shout out to Yesterday’s Tractor Forum and a quick tour of my shop. If you are interested, it’s at

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I’d sure appreciate your experience and opinions. That’s part of the trouble/fun with these sort of projects… in doing one you find 3 more you didn’t anticipate. I already got to change the ring gear which was not part of the original plan.

Thank you all.

Country Dabe

 

[m16ty]

Replace the plug. Is it a freeze plug going into the water jacket or the plug on the end of the camshaft bore?.
If it is in fact a freeze plug into the water jacket, you can just hit it with a punch on one side. That will spin the plug where you can just remove it with a pair of pliers. If it’s the camshaft plug, you likely won’t be able to spin it with a punch because the end of the cam will be in the way. You can still take a sharp chisel and bend the lip in to remove it.
For installation, first get a brass plug from the parts house so it won’t rust. Then put some sealer on the edge, find a socket that fits the plug, and drive it in. They are real simple to change out as long as you can get to them.

Edit- I didn’t look at the pics before I posted. That is a freeze plug into the water jacket. I’ll leave the above as is because the cam plug is still a thing on a lot of engines.

 

[Michaels Dad]

LIke m16ty said replace it now and save yourself a probable headache down the road.

 

[40Mule]

I would be careful if that is hidden after the repair or you will split it again also if your repair leaks. Holes are left in the cast iron block so the sand cores can come out, and any clinkers left in the block. What we call freeze plugs are machined in to plug the rough holes. While they may come out easy, they can be miserable and go in the block. At the engine plant we could turn the block upside down to get it out, hard on an assembled engine. We could pressure test the block after to make sure it was OK. I would think about the JB weld possibly because it is hidden and not leaking yet. If that is a cup plug, they were normally rolled to seal the wall. When we had a leaker, we could drill and ream the oversize or out of round hole and put in a bushing with loctite. Bushings came from a below zero freezer and expanded to seal. Then reamed to size using plenty of lube oil, and a chilled brass plug to finish. Brass plugs go in easier. feel kind of loose as they are soft, but were found to seal better. We could not repair on the rear of the block or behind the motor mounts because they could leak and warranty work. I have nothing against fixing them, just a little worried where it is at.

 

[Gary Reif]

Like was said above, just replace it. Use a punch to hit it on one side that will make it turn side ways. Then use a pair of channel lock pliers to pry it out then clean the bore. Then I always use some type of sealer, not silicone on the bore and find a socket that fits in the cup and drive it into place so that the edges are flush with the block.

 

[40Mule]

My concern is there could be corrosion of the block that cannot be seen at this point. If the plug corroded, is it rusted in also? I have taken stuff apart and wished I hadn't and admit it. It has been about forty years since on that repair job, but I still remember OR.. out of round was five thousandths of an inch. If you look at pic 2, it looks like a small amount of core shift. Clearance on the bottom below plug hole varies from side to side. Machining is locked in, but sand cores could shift where there might be less material than you think in there. I just tell this as general knowledge, not this block. I did not work there but have seen a lot of problems in 25 years in cast iron and five in lost foam and aluminum blocks. I just look at it as 4 small holes that could leak, or the circumference of the plug and a big leak. I do not want to be right, just avoid problems.