I’ve replaced my original OEM cooler with a Dorman Aluminum.

Everything

went in smooth, torqued to spec; However, when refilling my coolant reservoir I noticed coolant leaking from the top of the engine cooler, not the o rings, nothing in the valley.

in addition, I have coolant coming out of my oil pan. I’m assuming the coolant is mixing into my oil lines through the engine cooler.

Any ideas on what’s causing this?

 

Usually, that's a sign of a bad cooler........ or a failed gasket in the cooler.