All set to water cool and then a leak in my rad ...

There's basically a break in the seal between the barb and the rad .... how can I fix this? Just use some clear caulking? Thanks.

If you are not comfortable with a torch and some solder, I would use jbweld. It is every bit as permanent. It is a 2 part epoxy, that when dried, can be filed or sanded down it is so hard. If you can use a torch, submerse the rad up to just below the barb. Also, cover the rest of the rad with a wet rag so you keep the temps down on all but the area you are working on. Just warm it up some and flow a little solder, and it should be good to go.

I found that on my black ice rad, overtightening the barb can cause the O ring on the barb to unseat, causing it to leak. You might want to try unscrewing the barb and screwing it back in again. I found that I could get them tight enough by slipping some tubing on the end of the barb and hand tightening using the tubing as a grip.