I'm posting this because up until recently I never heard anyone mention to me that I should clean my vanos check valves. I didn't even know they existed!
I've been experiencing performance issues where it felt like the transmission was failing or I was having torque converter shudder. Low speeds around 1800 RPM under load was resulting in jerky acceleration and shudder and it was getting worse. Putting the car in sport mode helped with a smoother experience but it wasn't great. I thought for sure my transmission was going but it didn't make sense how some days were better than others and using sport mode mostly corrected the issue by increasing the rpm and power band slightly.
In the past I had vanos and ignition timing issues. Each time I've removed my vanos valves and cleaned them. I spoke with multiple dealers, and I've read many articles online about cleaning your vanos valves if you run into codes like p0012 or p0015. Not once did anyone tell me about the check valves!
Recently I was speaking with someone and they mentioned 'check valves' so I looked into it and wouldn't you know it there are two little valves hidden on the passenger side of your N52 head that you simply would not know were there unless someone told you. So, if you didn't already know about them, that's why I'm posting this.
In order to access the check valves and remove them it's easiest to remove your front passenger tire and remove the front wheel well protective cover. That will give you the space to access and remove them easily.
I have 250k on the clock and these were never cleaned! After cleaning them my performance issues are gone! The engine runs like new and I don't need a transmission service after-all!
I used this youtube video as a reference on how to remove the valves for cleaning.
https://www.youtube.com/watch?v=VQweif8dHFg
Also, here are a few images I took of my car and the valves before and after cleaning.
Inside wheelwell location
Check Valves
Upper Valve Filthy!!!
Lower Valve Filthy!!!
All Clean!
