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Chronic, Non-Obvious Fan-Belt-Consumption Problem

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#1 Pants


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Posted 24 March 2019 - 07:06 PM

I rarely drive my MK1 in recent years, and this is one reason why:  I've probably replaced the alt/fan belt four times in the last five years.  Original engine was replaced with a 1275A+ decades ago, but the belt-problem is relatively new.  Belt I've got on it now, I think the same as ever, is a Dayco 15320, nominal 32" (32.57" outside circumference.)  


My process is probably about the same as everyone's:  installing a new belt, I struggle a bit to get it over the alt pulley even when fully slackened (I usually push the car backwards in 4th gear to bump it over), then tighten by swiveling the alt up until it feels snug but not taught, retighten the alt bolts (which haven't slipped).  From that point, it charges fine and I hear no squealing, and I think everything's back to normal, and I'm wishfully proclaiming the problem cured. 


A few drives later:  voltage-gauge doesn't swing up out of the red zone, if it's in the evening, I notice headlight color is orangey, and maybe there's a tell-tale squeal.  I'll check under the hood and find that, sure enough, the belt is rattly-loose, and there's a fine black powder accumulated around the water-outlet, from the belt being reduced to dust.  I can retighten the belt once or twice, and all of the above repeats.


There's no obvious misalignment of pulleys, though at times while fighting this, I've been convinced enough that this was an issue to work in washers where it seemed they might be needed to improve the alignment.  There's no room to put any kind of straightedge down into the works to verify what my eye tells me on this, but I think my eye is pretty good - and my gut tells me that even a significant misalignment would take a few thousand miles to show up as a badly-worn belt.  I put maybe a thousand miles a YEAR on this car.


The pulley surfaces have, at times, appeared a bit rusty, so I went to the trouble to remove the belt and go over them with an air-driven fiber-disc, followed by epoxy coating.  No difference.


Water-pump spins freely, as does the alt - which I changed twice during the problem-period.


I do notice one thing that I've not yet run down:  rusty stains on the water-outlet bolts, as if it leaks under certain circumstances (never does so while idling with hood up, however).  I'm wondering if under some driving conditions, it could be 'lubricating' my belt by squirting out some coolant/water, but I don't see any big drops in coolant reservoir.


Anyone been down this road before?


Mahalo - Dave in Honolulu



#2 Moke Spider

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Posted 24 March 2019 - 07:33 PM

The Belt will tolerate a fair bit of misalignment from my experience. If you can 'eye' the pullieys in I would suggest that would be fine.


Other causes of premature Belt Failure are from overload, but you can usually hear it slipping, which you are not until it wears quite a bit.


The other thing is a worn Pulley(s). It can be a bit hard to pick up on and really, to see it properly, you need to use a V Pulley Gauge, it has a profile that is the Same as the belt, a bit like a Thread Gauge, but with only one 'tooth'.


One last item that comes to mind is a failed Harmonic Damper can also lead to belt failure.

#3 croc7


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Posted 25 March 2019 - 01:41 AM

Are you able to examine the belt for witness marks to tell where it’s wearing? I like Spider’s diagnosis-give the damper pulley a peek. Is there rubber dust down low as well?

Edited by croc7, 25 March 2019 - 01:50 AM.

#4 62S


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Posted 25 March 2019 - 09:16 AM

New belts do stretch and therefore need adjusting, I usually check a new one after fifty miles or so and again after another fifty miles by which time they are usually fine, and a little bit of dust off a new belt is not unusual. If everything looks normal and you are having to regularly adjust it, it would seem the belt is to blame.

Dayco is not a brand I am familiar with but a bit of googling indicates that some of their new belts are now made in China and if it is as good as the Chinese made Lucas branded ignition components I would definitely be looking for a different make of belt or a new old stock item.

32" is very close to 813mm which is a common belt length for a Mini so that sounds the right length.

#5 KernowCooper



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Posted 25 March 2019 - 10:28 PM

I'd be checking the damper and the pullys to ensure the belts not bottoming out and not driving on the V, all the belts your fitting can't all be faulty surely ? 12mm deflection on the longest run is the recommended tightness.

#6 GraemeC


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Posted 26 March 2019 - 06:38 AM

Is the V profile the correct one?

#7 carbon


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Posted 26 March 2019 - 08:48 PM



In your first post you mention that the 815 type belt is difficult to fit.


It could be worth trying the slightly longer 825 type as recommended by Minispares for alternator set-up: https://www.minispar...c/GCB10825.aspx

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