Soft plug, core plug, ?

[RTHarvey]

I originally posted this in the S10 forum, but no response, so I thought I would try it here, which is where I normally post (as I have a 67 C10). I fugure core plugs are about the same on any cast iron block:

One of the soft plugs (or freeze plugs or?) is leaking on my grand daughter's 1992 S10, V6. I think the manufacturer says that no sealant is needed, but that makes me a little nervous. Does anyone have advice on how to do this? Sealant or no? What kind of sealant? Brass or steel? Thanks in advance for any advice.

[sick472]

Brass has always been my preference and I always use some high quality high temp sealer (RTV silicone). I don't think there is anything wrong with steel plugs...it's really no big deal either way. Just put a very thin smear of sealer on the plug perimeter and the same in the hole...very thin is all you need especially in the hole. In a new hole with anew plug...no sealer needed, but sometimes the hole gets scarred by the removal of a steel plug and the sealer is good insurance. Most of the sealer will squeegee off when the plug is installed. That's why you only put a very small smear in the hole otherwise it will squeegee off into the block. That won't be the end of the world, but the less silicone buggers in the coolant, the better.

[HO455]

No sealant. Brass is my preferred choice. It won't rust through and start leaking. Make sure the hole in the block is clean. You will need a driver for the new plug that is the correct size. Then be sure you drive the plug in square to the block in both planes. They are a tight crush fit. Some S10 4.3 plugs can be a real pain to get to. This video might help.
Good luck.

https://www.youtube.com/watch?v=2zdnd5ikynU

[FirstOwner69]

I know I'll probably get "flamed" for this since the preferred cure is to replace the plug, however...

If the leak is relatively minor try some of this stuff first. I've used it several times over the years on different leaks (including a freeze plug), and it's worked well. It is an organic compound that does not gum up the cooling system like some other products do.

https://www.amazon.com/Genuine-GM-12...s%2C695&sr=8-2

[truckster]

I use Permatex aviation form a gasket as a light coating on the block opening. I prefer brass plugs, but I've used steel with no problems as well.

[RTHarvey]

Thanks to all for the advice. I'll let you know how it goes.

[CastIron]

Originally Posted by FirstOwner69

I know I'll probably get "flamed" for this since the preferred cure is to replace the plug, however...

If the leak is relatively minor try some of this stuff first. I've used it several times over the years on different leaks (including a freeze plug), and it's worked well. It is an organic compound that does not gum up the cooling system like some other products do.

https://www.amazon.com/Genuine-GM-12...s%2C695&sr=8-2

This stuff does work great for small leaks. GM has used it on new cars at times to reduce warranty claims.
If the leak is too big, of course replace the plug. It won't be easy with the engine in the vehicle though.

[Ironangel]

Originally Posted by sick472

Brass has always been my preference and I always use some high quality high temp sealer (RTV silicone). I don't think there is anything wrong with steel plugs...it's really no big deal either way. Just put a very thin smear of sealer on the plug perimeter and the same in the hole...very thin is all you need especially in the hole. In a new hole with anew plug...no sealer needed, but sometimes the hole gets scarred by the removal of a steel plug and the sealer is good insurance. Most of the sealer will squeegee off when the plug is installed. That's why you only put a very small smear in the hole otherwise it will squeegee off into the block. That won't be the end of the world, but the less silicone buggers in the coolant, the better.

This, but instead of silicon use this! A thin film on the bore and on the plug. https://www.jbtools.com/permatex-205...SABEgJmyPD_BwE I will also add that there are thin cheap plugs, stay away from them! Keep your old plug to compare thicknesses. Use a large 2" socket or the like to install the new plug. A quick rub with emery cloth to clean the bore surface, then a thin layer of the Indian Head and your golden...

[Steeveedee]

Originally Posted by Ironangel

This, but instead of silicon use this! A thin film on the bore and on the plug. https://www.jbtools.com/permatex-205...SABEgJmyPD_BwE I will also add that there are thin cheap plugs, stay away from them! Keep your old plug to compare thicknesses. Use a large 2" socket or the like to install the new plug. A quick rub with emery cloth to clean the bore surface, then a thin layer of the Indian Head and your golden...

Indian Head is the stuff! I used that and 3M Super Weatherstrip Adhesive (the yellow stuff, AKA "Gorilla Snot") to stick and seal gaskets when I worked as a mechanic ('70s and '80s). One of the other mechanics called any sealer "acka-pucky", and called me the "Acka-Pucky King", because if the repair came back for warranty work, it was going to be extra labor to get the "acka-pucky" off. I just said, fix it so that it doesn't come back for warranty repair on what you did. He didn't like that answer.

[BigBird05]

I worked for the factory and we always use sealer on the new engines.

[Steeveedee]

Originally Posted by BigBird05

I worked for the factory and we always use sealer on the new engines.

There was even a sealer that got slopped onto the exhaust pipes when they were assembled at the factory, at the muffler. I had the job right after that where I put the rear brake lines into the banjo fitting and put the brake lines onto the rear wheel cylinders. Tight, because the next cell pressurized the braking system, and if I didn't get one fitting tight enough, brake fluid sprayed all over the place.

[GASoline71]

I use "Indian Head" on brass plugs too.

Most leaks I've seen are from steel plugs rusting, or from new plugs (steel or brass) hammered in too far.

Gary