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Oil leak from engine bay

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Small but annoying one here. 

My 987.1 2.7 Cayman had a note of 'slight oil leak' at a recent MOT. It was annoying, in part simply because I hadn't noticed it as I haven't used the car much. 

So I jacked it up and had a look. Firstly, the oil filter housing wasn't screwed all the way home which explained some of the leak. But there was also a noticeably oily pipe in the top of the engine bay. Here's a photo viewed from underneath. 




When viewed from above it seems to be this pipe. 




For reference, this is stamped with part number "987 107 064 01" and a brief google search suggests that it may be part of the AOS. However the oil filler cap can be removed easily with the engine running which suggests that the AOS isn't failing. 


Having tightened up the oil filter the oil level is still dropping slightly (a recent 350-mile trip caused one bar drop on the dashboard gauge) so I presume that the problem is still there. 


Has anyone any experience with this? Is this pipe a regular candidate for causing problems? Or is it likely to be something else? 


All advice welcomed, thanks. 


(I posted this on boxa.net yesterday but no one there has come up with an answer, hence this post.) 

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Oily AOS tubing is common... Good preventative maintenance to change the AOS imo every 50k miles? ... You'll also need to remove all the associated AOS tubing and flush them with paraffin etc...

Was your last oil service done by you, an OPC or Inde?? 🤔


Anecdotally, the base 2.7 is far less prone to borescoring but if you are using a bit of oil & have noticeable smoke on cold start then a borescope of the bores will put your mind at rest imo 😉 albeit a failing AOS can also display these symptoms.


I'd give the engine a good degrease and observe weekly to ascertain where a potential leak is occurring?



Edited by Mavrik
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Hi, that pipe is the oil coolant pipe, I don’t think there’s always the same AOS symptom so could still be that albeit AOS has become the stock answer for a lot of faults as is very easy to DIY replace.


However if I’ve interpreted pictures right most of the pipe is saturated from beneath so you may want to give it a good clean with a degreaser then monitor as it could be the case of oil is being flicked upwards rather than dripping down.  Could maybe also be the oil filler pipe having a split or seal issue?

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Thanks for the replies. 


Mavrik, the last oil service (and the two before that) were done by me. I think that the AOS is original and I may well be tempted to change it anyway as it's 115,000 miles old. 


There is no smoke on startup (other than a small amount when used for short journeys, and that hasn't happened for the last 18 months as the usage of the car has changed) and the oil use has started recently. I'm not that worried about bore score. 


Acquell, thanks. The history is that the car had an advisory of there being an oil leak at the last MOT and the two things I could see were that pipe which is oily underneath and a slightly loose oil filter housing. The oil filter housing has been tightened but it still uses an amount of oil (I'm not sure how much because the segments on the oil level meter are a bit coarse, unlike a trad dipstick.) I'm therefore not entirely sure where it's coming from but that pipe is the best guess yet. Thanks for the suggestion that it could be the oil filler pipe - I'll have a look at that next time I'm underneath the car. 

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