I want an advise regarding following issue.
My mechanic noticed oil in the spark plug chambers (the external chamber). So he removed the engine head cover and replaced four oil seals with good Japanese seals. But few days after I noticed that there was oil again in the middle two spark plug chambers. Luckily the oil never went through the spark plug threads to the internal chamber. Oil remain in the external chamber. I have changed the oil seals twice, but still one spark plug chamber contains oil. However I weekly remove the oil from this chamber. But need an advise. What should I do.