Lister D oil filler cap

The oil filler cap on my Lister D leaks oil, there appears to be no seal on it, should there be, or is there another cure to try please.

It's normally a ground metal to metal seal, and should only be filled until the oil is level with the filler (with the engine on a level surface), so check you don't have excess oil in the sump. However, there is no harm in fitting a thin cork seal if there is a persistent leak, it will hardly be visible once in place.

Thanks for your reply, I think a cork gasket will be in order, the level is bang on, but when moving the engine around is when it dribbles a bit.
Many thanks
John

This was my solution 

https://ukengineforum.forumotion.com/t10985p25-my-first-lister-d#81642