Fan wobble a problem or no?

[wicks]

Hi - here's a video of my fan oscillating. It's a 34K miles car. I think the alternator was replaced by PO's mechanic not many miles ago, but some years (it was in collection, not used). I just replaced belt, and spinning the alt shaft, I noticed a slight oscillation of the fan, causing me to believe there is a misalignment in the hub for fan/bearing.

It doesn't appear to be a bent alt shaft as that piece stays true as fan oscillates...

[wicks]

Anyone? Or is this obscurity?

[SCOTITUDE]

Id pull the fan and alt and make sure that alt is perfectly seated in the housing. its a snug fit. could be a small peice of crud holding up one side. check the alt shaft bearing too. all done on the bench.
if it fails the scrapping sound you hear will melt your skin off. AHIK.

[wicks]

in the video you can see what's happening. Alternator mounted crooked can't be the cause.

[steely]

I don't understand how you can turn the pulley and shaft like you did the vid - and not have the fan turn with it.

Is it on some sort of clutch or is the woodruff key missing?
I do agree there's a wobble, but I didn't expect the fan to move independent of the shaft like it does in the video.

[wicks]

This is a 965 (turbo 3.6 1994) engine - m64.5o with single fan belt (thus a hub with bearing for the fan) and alternator driven by the A/C serpentine belt.

[steely]

aha - thanks for that info, sorry I couldn't help.

You might get better help on the 964 forum.

[brighton911]

Yes, to me that wobble has the look of a bent shaft.

[wicks]

Not bent shaft. Seems to me the hub bearing has to be crooked. No other explanation I think...unless anyone has a better idea.

[steely]

Try the turbo / 964 forum?

[Mixed76]

Bumping an old thread...

My 993 started throwing alternator belts. During troubleshooting I noticed that the engine cooling fan (belt on) wobbles when I spin the alternator pulley (belt off).

Original poster, did you ever resolve the issue with your 964, and if so do you mind sharing what it was? I can get a new fan bearing with insert from pelican, is a little expensive to just swap things out blindly.

Anyone know of a source for that bearing alone? Seems like the steel housing should be ok to press out and press in a new bearing.

Thanks,
Dan

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[wicks]

Hi, brighton911 was correct. Alternator shaft was bent. If you think about the physics of it, should have been obvious to me. A mechanic before I took over had to have somehow bent it.

I found a NOS unit online somewhere, and replaced the alternator and fan bearing. Fan bearing was very easy to get in place by freezing it overnight and having the fan nice and warm via heat gun. It is worth taking apart to confirm the diagnosis, since there will be corrosion on the shaft behind the bearing collar etc, which is good to clear out and put a bit of anti-seize on. Also examine the spacer on the shaft and clean up/antiseize, etc. You can also take the opportunity to get your fan nice and clean. Replacing the fan bearing could never be a bad investment either, since that failing can wreak all sorts of havoc.

[Mixed76]

Thanks for the reply! At present mine looks like a failing fan, there is a crack near the hub, rub mark on the fan shroud, and one fan blade with about a 1" chunk thinking about coming off. I haven't got it fully disassembled but I expect to find that the fan is no longer flat across the face. Will be getting the alternator looked at too.

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[wicks]

Ahh good thing you found the problem before the fan detonated in your engine bay possibly tearing a hole in your engine lid.