Radiator leak at cap

340Dart said

I have a Summit cross flow radiator which is stamped as a Northern radiator. I have had this for several years. Since I bought this most of the caps I tried leaked right between the cap and rad neck. I did have a NAPA cap that seemed to work but not any more. What could be causing this problem? It didn't do it with the stock radiator until I put this one in.

Fred B

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Same here , finally made a shim ,out of a plastic lid (two actually , made it the same size as the inner cap ,with close to size inner hole as possible , cut at a hard angle and screwed it under the original cap gasket , first time in 10ish yrS my recovery system has worked !
I made one for under the blow off gasket , and 2 for the rad seal gasket . Only problem is getting the size figured out .----TRY IT !