I have a 2000 4 lt.Jeep engine with NEW radiator freshly rebuilt engine no head gasket leak (tested)new water pump,new radiator cap(18lb.)and continues to blow out side freeze plugs..Sal C Cracchiolo

 

The factory used a 16psi radiator cap, not 18. I dont know if thats your issue, but you should be using a 16. Who installed the freeze plugs, and did they use the right ones? How were the bores cleaned? Were they cleaned? It is possible to remove too much material depending on how they were cleaned, causing the plugs to blow. Remove too much and they can work themselves out. If they were not pressed in straight, or bent, that can be a problem.

 

All very good questions you ask here. I always put 3M yellow weatherstrip adhesive on mine before they go in. We don't have a freezing problem here in the desert if it is maintained with antifreeze, but I think they would still push out if need be.

 

I use Indian Head Gasket Shellac on them. But fb brings up some good points. Sure hope too much material wasn't removed. Better chance of them just not being installed right hopefully.

 

He's also right about the cap. It should indeed only be a 16 lb cap.

 

Right. I'm just not sure if it would cause his problem. Read plenty of times where a 13 is called for but a 16 has been used. No blown freeze plugs though.

 

Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant, this is what an old engine builder I know told me to use years ago. But plug still has to be installed right like others have said.

 

I doubt the rad cap has anything to do with it. It would be blowing apart other things before pushing the freeze plugs out.

As long as they are set in straight and deep enough they should be good to go.
Ive seen people use sealant like Oswalla mentioned.. but I never have, just straight deep and tight
The brass ones are the best ones to use, not the steal ones.

 

"Freeze plugs" aren't actually meant to pop out when they freeze.

They're actually casting plugs. Tac weld the suckers in there.

 

Yep,, Ive froze a few motors up here in AK and not one popped out.. water pumps and radiators was the thing that broke.

I've been told the freeze plug holes in an engine block are a byproduct/necessity of the metal-molding process, right?

 

Yes. They allow the removal of sand once the casting has cooled down.

 

Ok cool, Ive always gone by that since I was told by an old mechanic friend.
But I have had people get bent out of shape when I told them the true purpose of them like I was told..

Meh! armchair mechanics mostly

 

I clean and lightly sand the opening and when I install the new plug I use red lock-tight , with more then 40 years working on cars I never had a plug come out .

 

Has anyone have a part # for freeze plugs and their diameter? I have a box of ten plugs which have diameters from 2.01 -2.05 measured cup down on a flat table and measured with calipers. Sal C

 

You make a good point here and I stand corrected, But I have seen them frozen and pushed out on heavy equipment and stationary applications. But what good they did... the blocks were also pushed out and cracked around the plug hole and needed to be welded up so they might as well have been welded in.