Okay, here is the deal. I had the same problem on my SHO back in November. It is comming from the oil cooler...which is where the oil filter screws into. The oring in the cooler where the cooler meets the bracket wears out for some odd reason. The problem gets even more interesting when you cannot buy this unique o ring from ford...only the entire oil cooler which runs $300 +. Paul Nimz has had mixed results trying to get a new oring from another manufacturer but they have leaked after installation. What I have came up with and has worked for me for 7 months and 10,000 miles so far is keep the same oring and put black silicone underneath where the oring sits. This will provide the oring to sit higher and provide adequate factory sealing. Also, I put a thin bead of black silicone all the way around the oil cooler as an added measure.
To remove the oil cooler, you have to take the oil filter off. Then, you will need a 30mm socket. I had trouble finding a socket for this job because you CANNOT use an impact socket as it will not fit up inside the groove to remover the bolt! I special ordered a non impact 30mm 12 point socket from sears. From here on out....it is pretty straight forward. Oh yeah, have a bucket ready to catch the anti-freeze from the oil cooler and the lines. Also, after the oil cooler is off the car, clean up where the cooler meets the bracket and where the oring sits in. Mine was pretty dirty. Good luck!
