It may be leaking between the camshaft cover and the head and dripping down into plug area. there's no gasket used here. It's easier to do if you gain access above engine to fix. there's two inspection caps that have rubber seals on the camshaft cap. I have used a crankcase sealer such a Permatex anaerobic sealer or ThreeBond to seal head and cam cover. Use very little and spread with your finger. If you don't have a service manual download one from Countrycat.com. At home page in grey bar at top under technical information.