Here's the stupid question for the day. Do oil cooler lines have a gasket, or are they some type of tricky metal-to-metal setup?

Both my 300SD's leak from the area of oil cooler line to oil cooler lock nuts. Is this where they usually fail? Is there a gasket replacement, or is the whole darn line that has to be replaced.

By the way, I just ran across a 83 300SD down at Frank's Foreign Cars in Laguna Beach that has 376,000 miles on it. The interior looked great but the paint was history.

83 300SD 176K
84 300SD 222K