968 belt squeal

[universeman]

Guys, I recently changed all the belts on the 968 without incident.

However, I cannot get the accessory belt (alternator/ac I *think*) to stop squealing under load, even though I have it tightened to what I think is a fair amount *too* tight (around 100lbs on the Krikit tool.)

I tightened the PS pump belt also, but that doesn't seem to be the one squealing.

The squeal stops when the engine warms up. It's only noticeable under rev / load, not at idle.

I don't want to over tighten and hurt the alternator bearings.

Has anyone else solved this problem? I am getting frustrated...the squeal is almost gone (like a little bird chirp now) but just won't quiet down!

[thomasryan]

check the ac/crank/alt alignment to be sure they are in the same plane.

from recollection, the belt is a similar deflection as the timing belt by 'tool' numbers. I count the turns between 5mm and zero deflection on that belt then go that many more turns on the turnbuckle.

when a car sits for prolonged periods, the belts, like tires, will take a set where it goes around the pulleys..ie flat spots. if you drive it for a few hours, the heat might make the squeal go away.

if you look at the ribs, see if the belt has been polished by being allowed to slip, you might just replace it.

[Jfrahm]

There is a spec for the 9201 for this belt and it is crazy high, 100 on the Krikit I believe is correct.
I do not crank it quite this high and tolerate a little squeak at startup.

There is an additional idler option via a modified alternator bolt. Adds a stud for an idler to get a little more belt wrap. You could probably also run a longer belt and come up with a different idler mount and get even more wrap. The belt tension spec seems high to me for happy bearings in the AC and alternator.

The belts run in and adapt to the pulleys fast so check the tension after a few hundred miles.

[universeman]

Thanks guys this is good stuff. I will keep working at it. Car has not been sitting more than usual (overnight etc.) Idler is an interesting idea. I'm not quite at zero deflection yet so sounds like I could go a bit higher.

[thomasryan]

from the manual...tension vs belt thickness.

[universeman]

Anybody got a 9201 I can borrow?

[universeman]

I ordered the 928 Motorsports alternator idler pulley mod - will let you guys know how it goes! Installing a new poly ribbelt tomorrow to see if the one I had just gotten too polished from slipping.

I was seconds away from ordering the turbo kit instead! Saved myself $4600 by not doing that But may be doing it soon...

[drkshdw]

Interested to see how the pulley mod goes. Thinking about it for my car too since it also squeals but mine is only at startup. It howls when driving and I'm pretty sure Joel is right and the high tension is making the bearings go in the alternator.

[universeman]

I swapped the belt and increased the tension. Squeal is gone. Don’t like how tight it is. Measured the distance between the pivot bolts on the tensioner (outside to outside) and it’s 12”. Was squealing at 11”...will update when I get the idler on.

[nyc951]

Subscribed

[universeman]

I added the 928 Motorsports idler pulley (mounts in the place of your lower alternator bolt.) Simple upgrade, does add wrap to the belt but not sure how much it helped the squeal - I still had to put some major tension on the belt to keep it quiet.

Now I'm hearing a knocking that I think is coming from the a/c compressor. That compressor leaks so I'm pulling it out to reseal it - I hear that the nose bearing can make noise when the seal is shot. Will update!

[universeman]

Rebuilt compressor, installed idler pulley, but chirp on the belt is still there after a bunch of tightening. Idler seems to have no effect. Rebuilt compressor no longer knocks/clicks. Going to try retightening belt tomorrow.

On a related note, adjusting hatch pins (simple) cured my hatch squeak. So I got one squeak gone, one to go! Belt is more of a chirp right now, when cold, under load.