Could be the endtank, but could also be the nipple for the vent line that goes to the expansion tank. I'd pull the shroud and take a look at it. Pressure testing the system may help you pinpoint the leak if you have access to the tool.

 

That nipple is on top, right? I pulled a couple fasteners and took a peek under the shroud and the rad was dry on top. Besides, if a vent nipple leak was that bad, it would drip off both sides, right?

 

It looks like it may be the bulkhead didn't get properly crimped to the core. Locating the source of the leak will give you the answer. You are pressure testing it when the engine heats the water.

 

That's what I'm thinking. There's no connection on that side but the upper hose and vent line, and they're both dry. Do they not pressure test rads before selling them? Or maybe it got jostled in shipping.

 

Who made that radiator?

 

It's a Behr radiator. It was double boxed with no visible damage.

 

Behr - that used to mean something. Behr Service - I’ve seen China and South Africa.