95 Sedan Deville Oil Leaking.

My 1995 Sedan Deville with the 4.9 had been leaking oil, and until recently, I haven't had a clue why, until I cleaned the engine, and the other day noticed the dirty oil spots on the engine and on the oil cooler lines that go from the engine to the radiator. I tried tightening them, and re-cleaned the area, drove it for 30 miles and inspected the area again. The fresh oil spots were clearly noticeable. Today, I took the lines off and inspected the o-rings on the lines, and they appeared in good condition, so I put some black gasket maker on them and reinstalled the lines. I don't know how well that will work, but time will tell. It was leaking from the oil filter part it goes into, then the middle where 2 separate lines meet, and where it goes into the radiator. Anyone else had this problem?

That is a fairly common problem on the 4.9. If your fix doesn't control the problem you might pick up some replacement O rings at the dealer. That normally resolves the issue. On mine I was lucky enough to solve it by just snugging up the fittings a bit.
FWIW
YMMV

I have a 94' and it was leaking around that area also. I followed the advice from this board and removed the air cleaner and found that the lines were fine. I snugged them up a little anyway. The fix for me was "over" tightning the oil filter by a turn or so. The leak has been gone for about 2000 miles. I guess I will see if it comes back when I change the oil next?

padgettra,
You might want to check the surface of the oil filter adapter at the next change. The might be a bit of old gasket stuck and a simple clean up might be the cure.
FWIW
YMMV