I heard someone talking about coolant leaking from a Catera at the rear of the engine but the water valve had already been replaced. I thought it didn't belong where I saw it so I thought I'd talk about it here.
On the top of the engine, in what would usually be a "valley" they installed a metal plate. This plate has sealer around the edges and bolts to the engine block but in it is mounted the oil cooler. Below the plate is coolant flowing through the engine to remove heat from the engine oil. Why they mounted this thing under the intake I'll never know, but needless to say if you have a pretty good coolant leak from this area it's likely this plate leaking.
You have to remove the upper and lower intakes and move some pipes, remove some banjo bolts and take off the coolant crossover in the back.
I have only done it a couple times so I'll post the images I think might help but this job is not for the timid. It could take you an entire day and if you mess up, you'll have to do it all over again, I'd advise finding someone who can work on this with some degree of skill.
Here are some images.