14 replies to this topic

[dansnyderECE2010]

So I bought a new alternator for my 89 mini and tossed it in.  Added a new belt and away I went.  I noticed that it was squealing a bit so I took a look and noticed that the blue stripe on one side was somewhat worn looking after just a few kilometers of driving.  I noticed after closer inspection that the alternator pulley was not centered on the fan pulley so I took it all off and put it back together with a  couple space washers to shift the top of the alternator to the right a bit.  I'm still hearing a squealing when engaging first or reverse gear coming from this belt.  Anyone else have this happen and figured out a solution?  Perhaps I just need to tighten everything a bit more although I tightened to 13mm of deflection like the manual says...

[KernowCooper]

Tightness is 12mm  in the factory manual and a new belt always stretches, if its aligned ok and set to the correct tension is the belt bottoming out in the pulley?

[cal844]

I run mine as tight as I can to start with!

[Tamworthbay]

The belt run doesn't need to be far out to get a belt squealing. Have you put a straight edge across the inside of the two pulleys? If you have was it bang on or close to?

[dansnyderECE2010]

Hmm, well, not sure if the belt is bottoming out or not.  I'll have to try with a straight-edge and see how off everything is.  Doing this never occurred to me.  Good idea!  While I'm doing that I'll have to test my alternator bearings.  Hope I didn't get a dude alternator...

[tiger99]

I have a suspicion that the alternator mounting faces, whether on the engine or the alternator itself, have a large tolerance, and they often need washers. They certainly did on one of my Minis, and I needed to change the washers to suit a new alternator. You will have noticed that the rear mount on the alternator has a split spacer which allows it to move in and out of its hole to take up variations in the length of the alternator or the mounting bracket. If the same sort of tolerance gets into the front mounting, you already know what happens. Strangely enough, I think that the old fashioned dynamos were more accurately made.

 

There are also shims behind the crankshaft pulley, and between fan pulley and water pump flange, on some cars. And therein lies a sad tale of incompetence and lack of quality control, at least in the late 1980s. They were leaving out the crankshaft shims in both new and Gold Seal reconditioned engines (I had one of each that was affected), and because of machining tolerances the crankshaft spigot was very slightly too long, so when the pulley bolt was torqued up it was only bottoming against the crankshaft end face, and not clamping the pulley, or the timing gear behind it, which both fretted on the shaft, leaked oil and gave various other problems. If spotted quickly enough, a large external washer cured the problem.

 

And, of course, some alternator pulleys may vary...

 

At least, once you get all the pulleys lined up, they will stay that way, and you will not have to do it again unless the water pump or alternator needs to be replaced.

[dansnyderECE2010]

I agree with you on the tolerance thing.  The alternator itself comes with one solid mounting point and a pressure fitting that slides back and forth about a cm.  That in itself assumes that there will be that much play in horizontal position of the top 2 mounting posts.  I'll work it out today and see if I can get the thing to stop squealing.

[dansnyderECE2010]

Okay, I tightened everything up and made sure everything was aligned more or less.  It seems that I can adjust to either have the belt slip (squeal) or the belt makes another sound.  May be bearings in the alternator, not sure but it sounds like a sweeping sound.  I took a video with sound.

 

Ideas anyone?  Could it be possible that my belt is on backwards or something?

[tiger99]

Your belt should be symmetrical, so can't really be on backwards. Inside-out perhaps, but I think you would have noticed that. It could possibly be the wrong belt.

 

You used to be able (presumably still can, although I have never used it myself) to get an aerosol which was intended to prevent belt squeal. Only in extreme cases, when all mechanical causes have been eliminated, would I suggest using such a thing.

 

A stethoscope, or long strip of wood, e.g. 2*1, placed against ear, or even a long thick screwdriver, will help you to listen to the alternator and water pump bearings. That will help to eliminate them as the cause. Please take great care to avoid accidents! (You could temporarily remove the fan to make it safer, the engine will not overheat when run for only a few minutes with no fan.) Placed on the alternator front casting, you can usually hear ball bearing type sounds quite distinctly.

[Captain Mainwaring]

V Belts don't stretch - they are designed not to, and when we transfer 100's of kW of power using them the setup is critical - they are purchased as matched sets, and when one fails they are all swapped out as a matter of course.

 

Tension and alignment are critical as is a belt suited to the application. The section of the belt is critical to match the design of pulley - get it wrong and it won't drive properly and will end up wearing the pulley sides out.

 

You probably won't get very far with some of the cheap rubbish on the market now. For the small added cost, buy Fenner or Gates.

[dansnyderECE2010]

Turns out the new alternator I got from minispares was defective (bearings were bad) but they're sending me a replacement in the mail for free so... go minispares!  Anyone have a good method of aligning all 3 pulleys?  Using a straight edge hasn't really been cutting it.  Considered getting a bit of wire wrapped tight over the pulleys to allow for me to more easily detect a misalignment.

[KernowCooper]

Mount it up and visually you should get some indication of alignment, you can use a 12" engineers rule on the pulleys if it looks out

[dansnyderECE2010]

Got the replacement and after some shimming I was able to get the darn thing aligned however now I seem to have another alternator issue..  The red light in the instrument panel (bottom left) is on now.  It goes dim when I rev the engine but stays on.  This is supposed to go out when the alternator is charging the battery right?  I checked the voltage at the battery while running and it seems to be a steady 12.43V.  Pretty low in my opinion...  I'd expect something from 13-14.  Thoughts anyone?  This is a brand new alternator.

Edited by dansnyderECE2010, 30 March 2014 - 08:14 PM.

[cal844]

Double check the connections at the alternator, i suspect it may be a duff alternator!!

[dansnyderECE2010]

Yup, just went out there and checked and all seems to be connected properly.  Tomorrow I can try slapping the old one in to make sure everything from the alternator to the indicator is working properly.  Dud # 2 would be frustrating....  Wonder if I can combine the components of 2 bad alternators to make 1 good one!

Edited by dansnyderECE2010, 30 March 2014 - 08:26 PM.