2002 coolant leak

On my wifes 02 Ls there is an intermitant coolant leak. It will leak out enough to run from the back of the engine to out in front of the car. I have looked and can see the area it is leaking in but can not see exactly where it is leaking. There is coolant on top of the engine just back of the air intake manifold and just barely up from the aft inboard side of the right head. This is the area where the heater hose goes into the firewall. What I would like to know is what all is in this area that could leak coolant. Again, this is an intermitant leak and seems to leak whenever it wants to like maybe once a week or every other week. Also the car has given an overheat indication, we had the car towed via roadside assist to dealer and they could not find any problem/leak and the system pressure checked good. I have checked the reservior and it is just a little low. My frind has an 01 Ls an occasionally it will leak coolant also. Again my main question is what all is in this area that could leak coolant. or does anyone have any diagrams/drawing of this area.