Yesterday after several minutes of idling and during low speed uphill crawling the car's temperature gauge started to creep past the midpoint. I stopped the car after just few dozen meters, before it even reached the next white mark in the gauge.

Today when investigating the issue I tried to replicate the problem of yesterday by letting the car idle for extended periods of time, tried also turning the A/C on and blocking the radiator with a piece of cardboard but the car didn't overheat this time. The coolant is topped and there are no leaks in the system, which leads me to believe the viscous fan clutch could be the culprit here. Also, for a past week or so I have heard some type of extra noise coming from the engine bay which to me sounds like it's coming from the fan, kind of like a failing bearing or something. I also noticed that the auxiliary fan is not working at all, or at least I was not able to get any type of reaction from it even with the A/C on, radiator blocked etc. If I recall correctly, with the E39 the auxiliary fan should make even some small movement when the A/C is turned on, not sure about the E53 but that didn't happen anyway. On the other hand, the outside temperature today was around 14 C (57 F), not sure if that is sufficient for testing.

My main question here is the reliability of newspaper test for the viscous fan. Today, after letting the car reach operating temperature, I rolled two newspaper spreads into a tube and stick it into the fan. In every test I performed, I was able to stop the fan with the newspaper. Although, I felt like it was little bit harder to do when I let my wife to raise rpm's but I was still able to bring the fan to a halt. Does this sound like the clutch is not properly engaging or is it completely normal to be able to stop the fan with the paper and the overheating was just because of the non functioning auxiliary fan?

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09/2003 X5 3.0i
02/2003 X5 4.6is (non-runner)