More than likely you have a leak in what GM calls an oil cooler, but is really a heat exchanger. It's located in the valley or the engine, under the intake manifold. It likely needs to be resealed.
If it can leak one way, yes it can leak the other. Just depends on wich one has a higher pressure. I did a little checking a some cases have it like yours. If it's different than before it has to be that or a seal problem.
I heard that the dealer has a new version that is not prone to cracking and is cheaper, around $180.00 but you need to check on that with the parts dept at Cadillac.
The used one may have failed when it got hot and under pressure.