As you may have just read I just done an engine swap, and I noticed when I got done driving it today it was leaking oil, I had taken the line off at the oil cooler. I just was looking at the FSM and it says there are suppose to be 2 seals on each side of the oil cooler, bolt. So I bought two new ones. My question is the line on the back of the engine does it, need two also. There is only one on it now, but it doesn't seem to leak like the oil cooler one did.

 

Replace all the crush washers, two on each fitting.

 

yep Banzai is right, you will need to replace both crush washers (two per fitting) everytime the lines get removed. You can try re-using old crush washers, but they always eventually seem to leak.