Freeze Plug Choices

[46BulldogDodge]

If the shoulder of the hole is damaged, you might be able to get away with JB Weld as a sealant when the new plug is installed since the cooling system is not a pressure system.  The less chosen, but successful for some guys, method is to use the rubber plugs that expand when you tighten the bolt through them.  Even here a little JB Weld around the circumference of the hole could seal the deal.

[Bingster]

Thanks. That's better news.  I have to wonder what the others are like.

[soth122003]

Clean it up with sandpaper, wire brush or what have you. The check how bad the damage is. If there is enough of the shoulder left you can apply a bead of pematex and install the plug. These flat heads are non pressurized cooling systems. If you think not much of the shoulder is left, you can apply a bead of JB Weld and install the plug and then apply another bead around the edge of the plug and let cure for at least a day before adding any water or anti freeze. 

 

My block on my engine is cracked right under the plug you're doing now. I was losing about a gallon every 2 weeks statically. With the engine running it doesn't leak at all. I used JB Weld to fix it  in May and it worked great...Until. This past winter in Jan the temps got down to 25 for about 2 days and the material difference between the cast iron and the JB meant that the cast iron contracted further than the JB. Basically the cast pulled away from the JB. It still leaks but only about a gallon every 6 weeks. My car stays outside all the time but I didn't think about the freeze while it was happening, until my water pipes froze. Took about 2 hours to thaw but luckily no pipes burst.

 

If your car will be in an unheated garage for the winter, be advised about thermal material differences. JB works great but does have some limitations. The engine heat won't bother it but the outdoor cold might. If there is enough shoulder use the Permatex. If you have to use something else be aware of this.

 

Joe Lee

[Sniper]

Or, if you feel lucky, you can use a dremel or similar to remove the remainder of the lip and use a cup plug.

[Bingster]

A cup plug. Okay. I was wondering about the difference in application between the dish plug and the cup.

[SteveR]

9 hours ago, Sniper said:

Or, if you feel lucky, you can use a dremel or similar to remove the remainder of the lip and use a cup plug.

I know I would not trust my skills in using a dremel tool for such a job. My experience is dremel tools bite when you don't want them to. It takes a steady hand.

[BobDeSoto]

soth122003

 

You stated back in October that the flat head is a non pressurized cooling system.

When I get back from a drive the upper radiator hose is under pressure. 

I did install a new aluminum radiator a couple of years ago.

It never pushes any coolant out the overflow tube or anywhere else.

The radiator cap came with the new radiator.

Let me know what you think.

[andyd]

BobDeSoto........my understanding is that the original radiator is non pressurized, ie it uses a 4lb cap whereas as you are using an aluminium radiator which is made for a pressurized system then you could use a radiator cap to suit that radiator..........but I would check with a competent radiator company or shop to be certain........andyd 

[soth122003]

Andy is right. The cooling systems were non pressure systems up to 1950, at least on the Plymouth. After 1950 they were installed to increase the pressure and raise the boiling point of the water. Since you changed to an aluminum rad, it has an overflow only when the cap pressure is raised and exposes the overflow tube in the neck on the rad. On the old rad's the overflow tube is at the top of the rad not in the filler neck of the rad. This allows the steam to gather at the highest point and then bleed of the pressure of the steam and not the water in the rad. 

 

The top pic you can see the over flow tube at the top of the rad and not attached to the filler neck. The pic on the bottom has the tube coming out of the filler neck. 

 

Hope this helps.

 

Joe lee

 

 

Edited December 22, 2023 by soth122003

[BobDeSoto]

So, since my car is a 1951 DeSoto, I can assume that the system 

is supposed to be pressurized.

 

Thanks

[soth122003]

Don't know for sure. My post reflects the Plymouth specifically and other cars generally. Your service manual will tell you for sure.

 

Joe Lee

[desoto1939]

according to my Atlas parts manual your 1951 Desoto would have used an R8 radiator cap. The R8 cap is a 4 pound pressure cap.

here isa picture of an r8 cap found on ebay. I use an r3 non pressure cap on my 1939 desoto.

 

Rich hartung

desoto1939@aol.com

 

[desoto1939]

I had posted this picture on the forum showing how to use a coffee creamer bottler to make it easier to pour distilled water into your radiator when you have a butterfly style hood instead of trying to pour the water directly from a gallon jug.  Also can use this method to pour water into each battery cell. Might take more time but you lessen the spillage of water and it is easier to control the amount of liquid being poured.

 

Always try to repurpose something to make your life easier when working on an older car.

 

Merry xmas to everyone.

 

Rich Hartung

Desoto1939@aol.com

 

 

[BobDeSoto]

From the shop manual:

 

Under normal operating conditions, pressure is not built up in the system.

However, if an abnormal condition develops, such as overheating, high

speed driving, etc., the valve at the bottom closes; seating against

the gasket.  This action pressurizes the system up to approximately

4 pounds, at which time the valve and seat raise and allow the built-up

pressure to escape through the overflow tube.