Magnesium valve cover n52 engine

[Dan McNulty]

Hello all, last spring I replace my valve cover with new gaskets, aluminum bolts, all genuine bmw parts due to a leal at the rear passenger side of the valve cover.
The valve cover came with a piece that I couldn’t find where to install but it looks like it might be pcv related.
I’ll try to post a picture of it.
Anyway me valve cover is leaking in the exact same place again! I was careful and used all information available on the torque and bolt torque pattern, ive been working on all my vehicles since I was young and have been able to successfully replace the other leaks on this car with no problems, ie oil cooler, oil filter housing, oil pan. Thinking this was pcv related i just sealed up a rubber hose into the hose that exits the rear valve cover and blew thru the hose with a very slight back pressure telling me the pcv valve is working. Spark plugs look to be firing great no carbon on them what else could cause this leak to reappear? TIA Dan

 

[Dan McNulty]

Unidentified part that came with valve cover

 

[Z4Mariner]

Magnesium VC here too. To clarify, did you replace the valve cover (VC) with one from another car ? If so, is there any possibility it is warped ?

When I replaced my VC gasket last winter, I notice something a bit surprising to me. The VC gasket was "glued" to the VC and lifted right off the cylinder head. As I separated VC and gasket, I noticed that there was something gray coming off with the gasket in patches, but not uniformly. My best guess is that the factory used a sealant on the magnesium VC, but not on the cylinder head. The date on the gasket was about two months before my E86's build date, so I think the gasket was original. I changed because the ESS sensor seal was starting to seep some oil

With no real guide, I cleaned the VC as well as I could, not wanting to sand into the magnesium metal. I used the thinnest smear of Permatex(R) Ultra Gray sealant on the entire mating surfaces of the VC to make sure there would be no gaps from a rough surface on the VC itself. I used no sealant on the cylinder head, which was fantastically clean. I put the sealant on just before before I placed the VC onto the head with the gasket in place. I installed the aluminum screws in two stages - finger tight, then initial torque spec - but NOT the extra angle torque. My E90 Bentley manual said to wait half an hour to add the final angle torque, so I waited about that, and then I gave all the bolts their extra angle. I have about 7K miles since then, and it's still dry.

Be sure that it is really the VC gasket - if the seal for your Valvetronic motor leaks, it can pool in the hollow of the VC under the motor, and it can overflow - so under some situations it might look like a VC gasket leak. It would be a shame to have to buy a new gasket and screws if it's leaking elsewhere and traveling.

Good luck on running this problem to a solution! Post back as you progress.

PS - I don't recognize that part - hope someone else can ID it