W212 E220 cdi - Inlet Manifold Query

[drosser]

I am fairly new to this forum and completely new to Mercedes cars. I have an issue with a turbo boost leak from the top of inlet manifold - 2013 E220 CDi. The air flow is emanating from a formed hole / depression on the manifold (located directly below the diesel filter housing - the hole is actually visible through the housing when the filter is removed). I am 70 years old and not 'tech savvy' when it comes to posting and uploading - I have photos but do not see an option to upload. I have attached a PDF file but have no idea how it will open within the post. Assuming it opens okay, it shows an overhead view of an identical manifold with the hole circled in red. Does anyone know what it's function is supposed to be? It obviously should not have an open port to the manifold internals. Could it house a pressure relief valve which has become faulty? Looking at Youtube, access to the inlet manifold is a bit of a nightmare so I would like to eliminate any simple options before tackling such a job. Would cleaning and infilling with a special epoxy provide a temporary respite whilst I consider options?
Also, can anyone advise the best technical workshop manual for the vehicle? Traditionally, I bought a Haynes manual for my cars but their product has changed in recent years - possibly not for the better. A friend (who is quite savvy with IT) bought an online manual which requires a VM but has not managed to complete the setup.

 

[PRSboy]

Cant help with your specific query on the hole, but my CLS 250CDI needed its inlet manifold replacing due to a leak. As you say, it was a nightmare to access and an expensive fix so I hope its nothing similar for you. The fault was diagnosed with a smoke test. Its apparently a common fault.

 

[drosser]

PRSboy, thank you for your reply. As you say, cracked inlet manifolds (and sheared manifold bolts) seem to be fairly common faults. However, there must be a reason for the hole - it creates a low spot which will, naturally, fill with any fluids and 'crud'. I was hoping that someone in the forum had actually seen a manifold or, even better, carried out work on them. Any experiences, facts or technical opinions gratefully received.

 

[drosser]

Looking at online photos, it appears that there is a fitment of some sort on the flange of the manifold directly opposite the aperture in question (see attached file). Could this a one way pressure valve which may not be properly seated. I've read that these inlet manifolds are often heavily contaminated with carbon. Does anyone know what the + shaped protrusion highlighted in attached file is.. A screenshot from a workshop manual would be much appreciated.