This coolant crossover pipe gasket leak has been a repeated and multiple vehicle problem with the 3.9L and 3.5L and GM only came up with 2 Technical Service Bulletins; the last one was #07-06-02-006E: Coolant Leaking from Engine (Replace Coolant Crossover Pipe Gaskets) - (Mar 5, 2012). However, the new gasket design presumably repaired the leak. However, it did not. I have seen this issue discussed on several web sites with all complaining about the same unresolved issue. My 2008 Impala with the 3.9L V-6 has been repaired for this issue on the following dates, each time I was assured it was satisfactorily repaired:

02/09/2019 11/30/2016 03/10/2014 01/11/2013

And now, it's leaking again! I chatted with Chevrolet online and this is what I was told after the first repair that warranty covered:

Cecil at 15:40, Apr 10: Unfortunately, once the decision is final that it cannot be changed anymore. But here is what we suggest, you can take the vehicle to a certified GM dealership about this to have it diagnosed and it might the same symptom but different root cause. We cannot perform diagnosis over chat.

Cecil at 15:41, Apr 10: And for assistance, I highly suggest that you speak with the Customer Experience manager or CEM at the dealership.

Now, the dealership is the one who told me that it could no longer be covered under warranty!

I hate to sell the car as it's excellent shape otherwise, but this issue is something GM should have long ago resolved with a better solution.