Ten raditor problem

I'm thinking the gasket material and sealer may not be rated for the temperature requirement.

Reminds me of a dumb move I made once. Used tar paper for gasket material on radiator......tar seeped out and made a mess along with some minor leaks that eventually sealed....won't do that again. 1/8 in. does seem a little thick.

Gean

I found my old radiator that looked good was leaking between the tubes and the top flange, I am guessing over many years of moisture getting in and freezing it seperated the solder Joints

I believe the original gaskets were cork, thicker and softer the better in my book.

Another issue I had is my bottom tank was not flat on the top, I had to cut almost a 1/8 inch off the center in the mill to make it flat, I am guessing warpage from prior repairs. It never ends on these old machines

Did you take the core to a radiator shop to get them to resolder the header? I lot of times the solder will work harden and crack. There may have been gunk filling the crack and now it is gone. I have always have taken my cores to radiator shop and had them boiled out and then resolder the header. I then reassemble using antiseize on all bolts. I then take it back to shop and pressure test and I haven't had an issue. I hope you are using the metal bolt strips that hold the headed to the tanks. I have tank apart a couple of CAt 15 radiators that do not have that strip.

John