1. Celem capacitors are manufactured with some oil inside them.
2. Oil appearance on external surfaces after shipping or storage is normal, due to internal capillary effects
3. During operation and under proper mounting and cooling conditions, oil might come out of the capacitor during the first few hours of operation. This is completely normal and caused by thermal expansion of the capacitor’s internal elements.
4. Continuous oil dripping, might suggest that the capacitor is overheated. Overheating can be a result of either improper mounting, problem in water cooling system, or electrical overloading. The cause of the overheating must be fixed, as the capacitor must not work in a temperature above the specification. (see Application note on cooling a capacitor)