I noticed last night on my 2004 998s FE the cooling fans have quit working. It over heated last night while I was stuck in traffic.
After I got home, I figured out the fans are no longer working. I checked the fuse and it looks ok. I am going to replace it anyway. This spring I had the Water Sensor Unit replaced because it was seeping. The fans were working fine until last night.
Any help would be appreciated.

Sounds like a bad connection someplace. Unplug each fan and see if they will run from an external 12V source. If you have a meter check to see if you have continuity in the connections. Sometimes the connectors will corrode and require cleaning. The fuses are also suspect. They can fracture and you have a hard time seeing the break. I had a fuse go on a 900SS and it looked fine but it was cracked. A meter can help here too. Sometimes the fuse will work when it is cold but as it heats up the connection opens and no juice.
Hope this helps