I have a 2006 Buick Lucerne with Northstar engine see signs of small coolant leak on garage floor & after a Pressure test I seen signs on top of tranny, but can't find that leak. Any thoughts on finding that leak, maybe where to concentrate on. Thought of maybe some kind of dye in coolant or maybe someone out there that may know a trouble site of where the leak might be from past experience with this engine. I knew from past experience with some Pontiacs 10 or so years ago had constant leaks from the split intake manifold. Any hints are gratefully appreciated!

If you can see coolant on top of the tranny. Good possibility its the crossover housing gaskets. Get it fixed soon, hate to see a headgasket blow on it.