My first M104, and I noticed that when idling and driving it has a pronounced whine coming from the front of the engine. I tried changing the belt, tensioner assembly etc, but the noise persists. Gets louder when I remove the oil cap.

I know this car has an intake timing cam advance mechanism, but I've never had it apart and don't really know how it works. Is there something in this area that could cause a whining sound of this nature that wouldn't warrant replacing the timing chain etc?

I also should say that I have a Check engine light on and its giving me a code 18: Intake camshaft adjuster Circuit. The car also hiccups sometimes and loses power for no reason. Every part (literally) of the ignition and fuel system is brand new, except for the fuel distributor. Very well maintained car, with all maintenance up to date.

I realize that a worn chain and/or sprockets could cause this problem, but is there anything that could cause an issue like this that has to do with the intake cam adjuster?

Thanks

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles