Auxiliary cooling fan impending failure?

[workingonit]

Originally Posted by 80stech

It's probably the viscous fan that you are hearing. Either way maybe check that the problem isn't vibration from something out of balance more than "loud".

Originally Posted by Bottomfeeder

Good counsel for sure. When I first heard the noise, I went promptly into "What the hell is that??" freakout mode and pulled over and popped the hood. No noticeable vibration ... just noise! Visibly, the fan seems to be operating as usual....

I had a noisy viscous clutch fan that worried me (though the clutch felt good? & just tight enough, I didn't want blades coming loose just now), so an electric fan conversion was my first priority. But, after I compared it to the still perfect viscous fans on my two trucks ('98 GMC 1500 & '04 Chevy Silverado 2500HD, the only vehicles I had not converted to or supplemented with electric fans, since 1990), I determined that it had too much play. As well as seeing it slightly wobbling and emitting a bearing-type squeal when running, and after I removed it, finding several blades that were chipped/cracked/delaminating, I was quickly sold on the electric fan conversion https://xoutpost.com/bmw-sav-forums/...ric-fan-4.html (my fan conversion tale starts with post #40). I also tested the auxiliary fan, and saw no problem with it, so it stayed.

The fan I used is almost as loud as the OEM fan I replaced, but in a reassuring way, at least to me. I set it to come on at about 183F IIRC, and in the two years I've had it, I've not seen the coolant temperature rise above 196F (after many stops in slow traffic, in summer). Normally, it has been at 188-194F, even during a shopping trip the other day, in 109F ambient temperature.

With this fan, the sound reassures me it's working (as does the coolant temperature remaining low, displayed on my Torque Pro app, on my dash-mounted tablet). I've had many aftermarket fans in 30+ years, with only two ever stopping (none permanently):[list][*]1) a Hayden fan blew a too small rated fuse, and the other time,[*]2) a Flex-a-Lite fan stopped when the "many-times used (on other projects)" relay failed (got a replacement immediately, as I saw the temp rising as I approached an autoparts store). I carry a complete set of fuses, and a brand new replacement relay, in the X5 trunk.

I never considered staying "stock" with a replacement clutch fan, since my X5 is my driver (though not daily) and project car...I have no need to keep it looking "factory", nor pristine (too late, anyhow), so I used the cooling fan solution that I always go to, that works for me.