Wierd... AC clutch noise after belt swap. Whats that about?

[billschroeder5842]

Huh, what would cause my AC clutch to start grinding after swapping a serpentine belt?

I'm chasing down (see other posts) a chirp-chirp under the hood. Here is what I have done:

1) new belt tensioner pulley
2) new AC bushing and cleaning of clutch surfaces
3) clean/light scuff of (with 600 grit sand paper) all spinning wheel surfaces
4) checked all spinning assembly with "the hose" method- all quiet

I put the old/new (4k miles) belt back on and got the chirp immediately. A few squirts of Windex and the chirp immediately disappeared. The chirp came back in a few seconds but the squirt of Windex quieted the sound right away. NOTE: the AC ran well and the compressor was quiet.

Clearly I had a belt issue, so I swapped the belt for an old belt (14K miles) for fun and to test. I started and the chirp was gone immediately. I went to test the AC and when I put on the AC, the clutch immediately make a grinding noise that was pretty constant. This grinding was consistent with the on/off of the switch and the engine was quiet with the engine off. My whole "testing" cycle was less that 30 seconds as I did not want to mess up the AC clutch.

So, what would causes with clutch to start making a noise? Is the belt pulling at a different angle (I'm not sure how)? Is the solution to tighten/loosen the nut on clutch or is this a new clutch and plate assembly solution?

This is just weird.

[billschroeder5842]

I had my buddy Allen come over last night for a second opinion. The belt is quiet but the AC compressor is very un happy when engaged. I'll be taking it apart in the next day or so and checking gaps, shims....etc.

[Erik]

That is damn strange. I?m curious to see what the outcome is.

[Undervetted]

Bill
I also chased a weird chirp on my 91. replaced belt, belt tensioner, ac clutch bearing. Finally replaced the AC compressor with a new Denso unit. Chirpping finally gone. Look if you see any oil coming out of the front seal of the AC compressor and the clutch magnetic ring .
Found the cheapest price at AMAZON. Denso 471-0337 comes with new clutch and pulley. Keep at it with 30 year old cars. The old AC was cooling fine before removal. I tried to drain the AC oil out of the old compressor, but it did not have any oil left and was dry. Good luck.

[billschroeder5842]

Thanks everyone. We put a new pulley on tonight and played around with different thickness/combinations of shims. Since I lost my feeler gauge (duh) we did everything by sight. Our logic was that we needed the minimum thickness of shim that does not allow for any contact while free spinning the pulley?

I of course obsess with the small amount of existing pulley "run out" from my bearing swap and worry that the clutch will not seat fully and slip. Is there a way to test to see if the clutch will seat properly before putting everything back together?

[billschroeder5842]

Well.... fail.

I put everything back together and fired up the engine. Completely quiet and smooth at idle but when I engage the AC, now I get a regular "rattle" almost like loose marbles. It is not a grinding noise but reminds me of the sound my old 81 BMW 320IS made when the AC was engaged. Plus, I get a faint (very faint) burning smell.

So, any ideas? I'm getting pretty good at "getting at the AC pulley" so I can have everything apart in less that 15 minutes.

I DID put a new bearing in the pulley a couple of days ago. The bearing and the snap ring went in place without a problem. I did notice that there is some kind of metal washer/sealer with a curved lip that (when installed) protrudes beyond the bearing by 1/16-ish of a lip. I did not think much of it as it seemed to fit in place "normal" when I installed- I thought of it as some sort of seal. Should that be flush against the bearing?

My wife is out of town visiting her parents so I (mercifully) have a free weekend to fix this thing. I'll have time ti get into the FSM.

Any advice is appreciated.