Remove all the IC hoses and check for leaks. Being over 10 years old no doubt the IC hoses will be worse for wear.
If your IC is leaking you will see it. Check the top of the engine for oil deosits and check the under side of the IC for oily patches. Number one visual give away of a leaking cooler. If its the EGR, usually, it will give off a squeal when the engine warms up. Like I said, usually. Some have mistaken the EGR leaking for a belt squeal.