Radiator Bolster Drain Plug Seepage - My Solution

[lyle11]

I have one Cub that seeps around the radiator drain. I have used this method 3 times with good success to stop the leak. I just changed the coolant the other day. What I do is to fill the hollowed out part under the clean, dry drain plug with a gob of the Permatex silicone in the attached photo. Then I smear it over the last couple of threads. I install the plug and wait 24 hours before I fill the radiator.

When I remove the plug, the silicone comes out like in a little firm bullet shaped plug and it’s easy to remove any that remains on the threads.

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[ricky racer]

Thread tape wouldn't stop the leak?

[lyle11]

Thread tape wouldn't stop the leak?

In my case I couldn’t stop the leak with thread tape. I realize that’s a much cheaper solution unless you have silicone sealer laying around. I don’t think there is anything special about the Permatex stuff I used and probably most any silicone sealer will work. I have had good luck with this method and have had a 100% seep free plug until the next coolant change. I’m just presenting it as an alternative method if you have seepage at the plug. If thread tape works then by all means use that instead.

[tst]

correct pipe plug 3/8 " NPT ?

[staninlowerAL]

The threads on mine was in very poor condition. Here's another way to fix the problem without drilling and tapping. Sorry for the orientation.

[NJ Farmer]

I recommend TFE paste (little can with a brush in it) found in either your automotive or plumbing section of your favorite hardware shop. TFE paste will withstand pressure (which our systems don’t have) but will also make it easy to remove the plug over time. It seals and “thread” imperfections and is used in high temperature situations ie heating systems in homes.

Anyway my suggestion and it works in my tractors.

NJ Farmer

[NJ Farmer]

I would like to also recommend a brass plug if the old plug is bad. Steel plugs will rust out and can cause pain and headache trying to remove
down the line. Brass is soft so don’t over torque since it will fail before the cast iron bolster will. Again put TFE paste on the threads before install.

NJ Farmer

[john2189]

Permatex aviation cement is good too. It seals and stays soft

[SamsFarm]

You can always chase the threads in your cast iron with a tap.

Since it is a tapered thread, you can freshen up the threads by going in a little deeper.

But dont go too deep!

[Bennydh]

I had a seized plug on my 48, I even welded a bar to it to try to break it free after the head rounded over. No amount of torch, or penetrating fluid made a dent. I finally sheered the old head off trying to turn it out. I ended up drilling it, tapping it, threading a bolt through it, and then welding the bolt into the place so that I had something to mechanically turn it out. It was one of the most heinous bolt extractions I've done.

Fortunately, the threads were good, I chased them with a tap, and I ended up putting a brass plug w/stopcock on it.

If I were in similar shoes, and either tape or paste didn't work. I'd consider drilling and retapping. Maybe just retapping to the slightest increase in size, just to be able to get a snug fit with a brass plug.

While it may not be original, brass is so much better for this application. IMHO

[Matt Kirsch]

It may be just me but the plug in the first picture looks like it is completely stripped of threads. If that is the case, no wonder it won't seal.