Originally Posted by BimmerM3inGA

bcredliner: VANOS failure won't result in a meltdown. Just a lot of noise and a crappy idle. I'd be more concerned about a stretched and loose timing chain than the VANOS. I know what you mean about the instructions just being academic until you actually start turning wrenches. It's the same for me!

If you do decide to pull the trigger on the timing chains and guides, it would be wise to do the VANOS at the same time. Even if they don't need it. You have to take all that stuff apart anyway, so you might as well take care of that at the same time. The rebuild kit is kind of pricey, and the seals are not nearly as easy to replace as on the I6. But it's still a hell of a lot less work than having to come back and do it later…

JAX01X5:Yes, the markings on the square (rearmost) end of the cams face up with the crank at top dead center for cylinder #1. FYI, cylinders 1-4 are on the passenger side with 1 at the front and 4 at the back. 5-8 are on the driver side with 5 at the front.

The shutter plate ("timing wheel" in BMW-speak) is held on by that reverse-threaded nut. If the nut is loose, the cam position sensor won't know where the cam is, but the cam will still turn with the chains. That nut isn't what secures the cam to the sprocket.

When I bought my 740i, the racket from the engine was unreal. It sounded like a diesel with a screwdriver loose in the crankcase. It had the triple-whammy of totally disintegrated chain guides, stretched chains and the VANOS death rattle. And the car only had less than 150K miles. There was a handful of plastic debris in the oil pan. In hindsight, it was probably unwise for me to have driven it the 10 miles to my house after I bought it. I should have trailered it. But I took it easy on the drive and I guess I got lucky.