Oil leak between oil filter and engine block on 1993 Honda Accord

I'm guessing it's coming from the part that's between the engine block and the oil filter. I took off the oil filter, there's a 30mm size nut but I don't know if the nut is removable.

1 answer
The part is the oil cooler. The nut is removable. You'll need to replace the O-ring between the cooler and the block, the sealing ring on the bolt (if equipped) and I would replace the coolant hoses to the cooler too.
Here is a pic: http://img45.imageshack.us/img45/8453/13ss00a05xf7.gif
#18 Oil Cooler, #19 bolt, #33 o-ring