Hi folks
I am fully aware of the issues with the 3.1L/3.4L intake gaskets. My question is, how can you tell if it is leaking?
-Rad pressure test?

I don't believe I am losing any coolant, but during my oil change today, I noticed a slight milky white substance on the inside of the filler cap.

There don't seem to be any external leaks (no coolant puddles in the V)

thanks for any advice

If the gasket is leaking you will see a coolant loss. A pressure test will help but usually these gaskets leak once the engine has heated up. The oil itself will look like chocolate milk and the engine will not run correctly. The white substance you are seeing is normal especially if you use the car for short runs. At this point I really don't think you have an issue.

I wouldn't be so sure...the white substance on your filler cap is what happens when the coolant mixes with the oil. Look in and see if you have more white suff in around valve springs. This was my first symptoms when mine leaked. A very little bit of white can be explained by moisture in the oil, but I would pay very close attention...there is no use in waiting...it's going to go so better to fix it now.