For almost a year now my 2004 Excursion Limited 6.0L has been leaking some anti-freeze and cannot find out where it is leaking. I have taken it to the dealer twice and they cannot find out where it is leaking. I have been up under it and cannot find out where it is leaking. It's not leaking a ton and it is not doing it every day. Just a small splash except for the other day and it was more than a splash.

I took it to the dealer on Monday and they put 18lbs of pressure on the system and the mechanic who has 10 plus years experience at the dealership said he cannot get it to leak.

This weekend we went no where in it. It sat most of the day on Saturday except for the less than 1 mile drive to take my daughter to work I then backed it out of the garage and let it sit in the driveway while I was doing something in the garage. It was in the driveway for about 2 hrs. Then I pulled it into the garage and on Sunday did not drive it at all and then came out on Monday morning to a more than just a splash of fluid. It was a pretty good amount so I drove it to the dealer and after spending $49 and more than 3 hrs wait time they still cannot figure out where it is leaking. The first time I noticed the small puddle was back in January when I immediately took it to the dealer and they couldn't see where it was leaking then. I have been topping off my coolant regularly but nothing that amounts to anything. I have had a gallon of coolant in my garage for more than a year and it is still pretty full. I can't figure this out and it is really frustrating.

ANY ideas?? I know it is not freeze plugs, doesn't appear to be water pump or anything like that. It is leaking on passenger side. Again not very much and not all the time.

Thanks in advance for your help.