I am on the verge of buying my first Porsche. A 911 997 c2s. However this ongoing problem with the rear main oil seal and intermediate seal is concerning. The car does come with a 12 months or 12000 mile parts and labour warranty. After that i'm on my own. Is this some thing thats happens to all water cooled models? and is there any external signs to look out for? I would appreciate your advice.