Clearances are too tight between the connecting rod bearings and crank journals which results in reduce oil flow, causing premature wear and eventually failure. This creates metal shavings which damage the connecting rod bearings and other engine components (such as the high pressure oil pump and the VANOS actuators).
If they are not replaced preventatively, the rod bearings can completely fail and cause catastrophic damage to the engine.
It is highly recommended to have an oil analysis performed after every oil change. If tin and copper content in the oil spike, it’s time to replace the rod bearings.
VANOS high pressure oil pump failure – can cause catastrophic damage if the engine is not shut down in time. Replacement cost is usually around ~$2000 for labor and another $1400 for a rebuilt pump. Metal shavings from failing rod bearings can cause premature wear/failure of the oil pump as well.
Throttle body actuator failure – rebuild kits are available for $120 each (there are two). However, the fix requires removing the intake manifold.
MY06 and earlier: A fault in the VANOS high pressure lines can cause them to fail and erupt oil, resulting in catastrophic engine damage if the engine is not shut down in time. This can often be mistaken for high pressure oil pump failure, but is far less expensive to fix. In either case, the high pressure lines should be removed and pressure tested to confirm where the issue is.