Leaking Freeze Plug

The freeze plug next to the right motor mount on my 91 dodge 1/2 ton truck with the 318 decided to take a crap almost leaving me stranded. While looking for a replacement, I did not see any stailess steel plugs which is what I would prefer to install. Found steel and brass in both deep and shallow. I’m leaning toward the brass. I also found expansion type plugs that are bolted down the center. Are these reliable or more of just a quick fix? Need to get this fixed asap as this is my money maker and just looking for some insight.

I used the expansion type of plug on a car I had and kept driving it for another several years, never giving it another thought. I also used one of these plugs once to fix a hole at the bottom of a commercial stainless steel 3-compartment sink after we moved it and didn’t need whatever accessory passed through there. (I don’t remember why any more) That repair lasted many years and may still be going, but I got out of that business.

My only thoughts about brass vs. steel are that brass may not expand/contract at the same rate as the steel plug, and there may be some kind of electrolysis effects that corrode the block around the plug, while a steel plug may be prone to rust. However, either would likely last the remaining life of the vehicle, as no doubt an expansion plug would too.

Removing and installing freeze plugs can be a difficult job, especially in 22 year old trucks…I would go with the rubber expansion plug as they are considered a permanent repair…Don’t be surprised if more of those plugs start leaking…

I have never seen a stainless steel freeze plug, I have only seen them in brass and aluminum. Aluminum has been used in all engines from the factory since the 60’s, prior to that, brass was the predominant material for freeze plugs. I have never had a problem using either as a replacement, never tried the rubber type so I can’t say anything about those.

If you have an aluminum radiator, you need to use the aluminum freeze plug, not the brass.

I would not worry about getting the old plug out either, I always just knocked them into the block and put in the new freeze plug. The old one will settle to the bottom of the block where it won’t do any damage, at least that is true on old American iron engine, not sure about the new all aluminum engines as teh blocks don’t have the deep water jackets the old engines had.

Aluminum? All the freeze plugs I dealt with were steel, in the 70s. I would think aluminum would create the risk of electrolytic corrosion in an iron block.

I’ve never seen an aluminum block plug; only brass or plated steel.

The ones I replaced, I was able to drive a narrow-bladed screwdriver through the corroded metal and pry the remains of the plug out of the block. They appeared to be steel, as they were rusted.

The plain steel freeze plug will work fine and certainly outlast the other freeze plugs on the engine. The only reason to use the rubber plug is if you don’t have room to drive in a new steel plug. I also never had a problem removing om
e by punching through it with a hammer and screwdriver and prying it out.
I usually used an appropiate length of a wooden broom handle to drive in the new one.

I stand corrected on the aluminum plugs, I think they were aluminized steel, that is steel with an aluminum plating to resist corrosion, they had an aluminum looking finish anyway. But I still have never seen a stainless steel freeze plug. The reason you would never use stainless steel is because it is a less active metal.

If you are going to get dissimilar metal corrosion, you want the removable part to be made from a more active metal. A freeze plug is cheaper than an engine block.

It has been a long time since I have had to deal with a freeze plug and I pretty sure I recall seeing aluminum plugs. The last one I changed I think was on my 66 Dodge back in 77.

Changed the offending plug…While underneath the “beast”, found another freeze plug that had a small defect. Changed both plugs with the regular coated steel plugs. Double flushed the cooling system and filled with fresh coolant. Back to normal operation.

At least it wasn’t one of the plugs behind the flexplate or flywheel as the case may be… :slight_smile:

Even if it was behind the block on the automatic 3 speed stock set-up, I would still take a day and remove the trans and get her back on the road.