Fan scraping - quick thoughts?
 

I recently replaced my fan housing with a Carpoint housing because it was cracked and the fan was ever so slightly scraping at around 630-7 o'clock position.

Prior to doing this (and about 5000 or fewer miles ago) I installed a classic retrofit alternator (excellent upgrade, btw) with the appropriate spacer. Bearings should be in great shape.

Fast forward, new fan housing and belt (might as well replace the 2017 vintage that I was using) and I have scraping at the same 630-7 o'clock position. I've played with the shims and am currently at 2 out, 4 in, and if I go any looser (1 outside and 5 inside, I think) I get very bad squealing.

I have plenty of clearance on the top side of the housing using a feeler gauge, but can barely get a .010 feeler gauge in at the point where it's scraping. I get no scraping whatsoever with the belt off.

My initial thought is that maybe I over-tightened the one alternator nut (that I think is at 6 o'clock) that's not holding on the alternator cooling shroud. The shroud is original and kind of flaky, so I was pretty gentle tightening those 4 or 5 nuts, but they are tight nonetheless.

Before I take the housing back out and readjust the tightness on the alternator bolts, anything that I'm missing? Is it worth trying new shims if the old shims appear to be flat/not distorted?

1. Alt pulley is relatively new (20k miles) and in good shape.
2. Fan housing is new - no scraping with belt off
3. Alt is relatively new - bearings should be in good shape and no noise with belt off
4. Shims and conical washer appear to be in good shape
5. Fan strap definitely not too tight - I only have a few threads on the bolt exposed.

#5, fan housing strap is to tight. Make sure the fan housing is lined up and keyed into position. If it isn’t seated properly, and over tightening, can create the symptoms you describe.

How much space between the alternator and the fan housing. Is it possible to shim your alternator in the opposite direction of the rubbing? Maybe it's machined on the small side. A thin stip of adhesive aluminum tape on the bottom of the alternator will shift it up in the housing.
That's what I would try.
David

I installed the Classic Retrofit Alternator a couple years ago, and mine doesn't scrape, but it's real close at the bottom of the fan housing. I wondered the same thing about the bearings, but since it's not scraping, I'm just running with it. Too many other projects to pay attention to.

I don’t think it’s the fan strap - I just tried marking hosing with sharpie, loosening the strap to the point the housing is still firm but I can still squeeze the strap ends together and still getting scraping.

That’s an interesting point about shimming the alternator within the housing. Seems reasonable but I’ll be the first to admit I’m in no hurry to take the alternator back out.

Any thoughts on the pulley shims, or any pulley parts, being a potential issue?

+1 on the over tightened fan strap. Easy to back off in order to see if that cures it before going down the rabbit holes. Worked for me...

I spoke too soon. I was messing in the engine bay tonight and checked the fan. It's beginning to rub at the 4-5 o'clock area. One more damn thing to do...

I have the fan strap barely fastened and will give it a try. With the belt off and strap barely tight (i.e., bolt not threaded all the way through, but housing still firmly in place), there's still a noticeable difference in the spacing between the fan and shroud at 12 o'clock and 6 o'clock. I assume this is generally supposed to be concentric all the way around, but any thoughts? I didn't have time to reinstall the belt and give it another check yet, but am thinking this probably points to fan strap not being the culprit.

Would a mal-aligned woodruff key from installing the fan to alternator cause this? With the belt off and one hand firmly holding the housing, I'm not getting any flex when I push up on the fan at 12 o'clock. Maybe an extremely thin shim washer at the 6 o'clock bolt?

Check the alternator nuts on the back of the fan housing. Sometimes the fan is in a little cocked to one side and you can't see it. Make sure all of the nuts are tight and the alternator is seated properly at each nut. If it is hitting at 6 then the nuts on top at 12 most likely need to be tightened more. You should mount the fan with the housing out of the car, tighten the alternator and see if it is still scraping. That will narrow down the issue

Agree with Mike, had a small interference on mine, my cooling duct had some cracks at some of the clearance holes. Turned out that pressure was not even across the mounting bolts. Used slightly larger washers and this cured the interference issue.

i tell you something you might not like ..?;-)
.Back in the 1980`s we had several problems with alt.hitting the housing All checked ,nuts tight ,bearings good.What we have found was that the housing got squeezed to tight by some mechanic in our area of Woodland hills. and the housing was not round..so..we use copper hammer and hit the housing (gently not to hard not too soft ) and noise was gone ...about 3-4 cars..
Ivan

Along with the usual cracks in the mag housings, the surfaces can erupt in bumps from the mag shape shifting/rotting. On my last '89 top end job, i had to use a small 2" air grinder to level out several internal knobs so the fan blades would clear.