Fanbelt keeps losing tension.

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SimonB
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Fanbelt keeps losing tension.

Post by SimonB » Fri Apr 18, 2014 2:40 pm

Hi, I know that this is a really basic question but it has been annoying me over the last through months. I keep setting the fanbelt tension and then it slowly (and sometimes not so slowly) works itself loose, squealing and once even managing to work itself off. I do not want to set it madly tight as I know that this will wear out the water pump and possibly the alternator too. At the moment the adjustment on the alternator is just a simple nut and bolt, should there be washers and a lock nut to stop it slipping or could there be something else going on? I know this should be really simple and idiot proof but there you go...

Its my usual Alfa GTV6 2.5 from 1984 that I have had for the last 16 years or so, never had problems with the fanbelt until recently.

Thanks for any tips...
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Re: Fanbelt keeps losing tension.

Post by SimonB » Fri Apr 18, 2014 3:14 pm

And another thing, why do some shops give an 825mm belt for these cars when an 850mm one fits or does this vary from version to version?
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Re: Fanbelt keeps losing tension.

Post by fedezyl » Fri Apr 18, 2014 8:25 pm

How old is the belt? it may be a poor quality item, the belt should not be super tight.
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Re: Fanbelt keeps losing tension.

Post by kevin » Fri Apr 18, 2014 11:04 pm

Simon you mention its just a simple nut and bolt but all three bolts must be tight ( carefull one into water pump) . Once you have set the tension and tightened with the the size 13 on the bracket then you must make sure the 19 mm nut on the bottom bracket is very tight . If that is loose then the alternator will come loose every time from vibration . The vibration even wears the casing oval for the bottom bolt which may in future prevent it from remaining tight over time .
Make sure on top bracket you have at least a 20 mm washer and the nut is either a nylon locknut or has cerrated backing to it to prevent the vibration working it loose . Factory nut had a cerrated edge washer nut combination .
DONT tighten the the bolt onto water pump to tight ie just firm as you definetly don't want to strip this .
Next time belts off spin the alternator pull to see if bearings are not badly worn and if the shaft has excessive play which can cause vibration .
Note its painful to tighten bottom bolt but with correct sockets and spanner jammed into position underneath you will get it done . Note there should be a a washer on the bottom nut as well and its also nyloc nut .
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Re: Fanbelt keeps losing tension.

Post by SimonB » Fri Apr 18, 2014 11:47 pm

Thank you Kevin, these nuts and washers are just the sorts of things that can disappear over time.
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Re: Fanbelt keeps losing tension.

Post by SimonB » Sat Apr 19, 2014 12:42 am

So, assuming all the nuts, bolts and washers are rubbish, what should I buy to sort this out? I am not very good with all the M numbers and stuff. Otherwise I'll just go to a hardware shop with the old ones. Cheers again.
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Re: Fanbelt keeps losing tension.

Post by SimonB » Sat Apr 19, 2014 12:44 am

The belt is new but might not be the best quality, I have just ordered an OE quality one, but I think its probably the old nuts, bolts and washers that is causing the problem.
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Re: Fanbelt keeps losing tension.

Post by kevin » Sat Apr 19, 2014 3:36 am

I would use grade 8.8 bolts . The size is 8mm diameter with a 13 mm hex head . Probable about 25 mm long . Thread pitch is standard at 1.25 mm .
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Re: Fanbelt keeps losing tension.

Post by SimonB » Mon Apr 21, 2014 10:06 am

Thanks Kevin, better nuts, bolts and washers have been ordered. Bottom nut wasn't that tight so thats a good tip too.
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Re: Fanbelt keeps losing tension.

Post by kevin » Mon Apr 21, 2014 1:21 pm

That's definitely the main problem but with that tight and the correct nuts and bolts washers etc it won't come loose Unless you have a broken right engine mount and when doing hard track sessions the alternator make contact with the castor arm housing . It happened to me but it usually results in the cracking of the housing at the bottom .
Just put small mirror down and check for any cracks anyway .
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