Any pneumatic nailer has O-rings that eventually wear from use or lack
of lubrication. Some of the Senco's are designed to work without
lubrication. WD40 is too thin - any home center will have nailer oil
in a small plastic bottle. Take the nailer to a repair shop and either
get them to order an O-ring set for you or let them repair it.

On Wed, 18 Oct 2006 06:27:46 -0500, wrote:

I just got a Senco - model SFN2 air nailer.
I found it at an auction and it sold real cheap because there was a
sign on it that said "Needs Work". All I had to do was put a little
WD40 in the air fitting and it works fine.

The only thing, it is constantly leaking a small amount of air from th
exhaust port on the "head".
What could be causing this air leak?

Mark