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noexit
Samba Member
Joined: September 18, 2006
Posts: 329
Location: Tacoma, WA
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 Posted: Thu Oct 26, 2006 11:46 pm Post subject: Belt: How tight? |
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My 74 Super seems to be eating belts. Last week one went out as I was going down the freeway. Later my dad called and said he had tightened it when I was at work, got it too tight, then forgot to loosen it again.
So when I got the new one, I tightened it as tight as the book says, so that there's 1/2 inch or flex when you press on it, but it seems to be eating this belt too. Pushing on the belt doesn't seem to be too precise. How tight should it be? |
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DMC-12
Samba Member
Joined: September 19, 2006
Posts: 817
Location: Maryland
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| Posted: Fri Oct 27, 2006 4:13 am Post subject: |
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| You may have an incorrect style of belt or it may be out of alignment. |
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ed stanley
Samba Member
Joined: September 28, 2006
Posts: 508
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| Posted: Fri Oct 27, 2006 5:02 am Post subject: |
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| 1/2" of flex should be about right. Also, you should be able to grab the belt halfway between the pulleys and be able to turn it 90 deg with your fingers. Too tight is awful bad on the alternator bearings. Lost a new $100 alternator myself with too tight belt. Also, check your pulleys - if they're rough and rusty where the belt goes, it will eat up belts. Clean 'em up. |
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68Bug-lite
Samba Member
Joined: July 31, 2005
Posts: 1087
Location: Tustin, CA
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| Posted: Fri Oct 27, 2006 5:50 am Post subject: |
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Are you putting the unused washer/spacers on the outside of the pulley? Went through a few belts and pulleys not having them there  . |
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Aussiebug
Samba Member
Joined: June 03, 2002
Posts: 2162
Location: Adelaide Australia
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| Posted: Fri Oct 27, 2006 6:37 am Post subject: |
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Do you even have the correct belt?
The cars with generators use a 905mm x 9.5mm belt. About 4-5 hp flows through this belt (the generator's output plus the cooling fan).
When the alternators were introduced in 1971, the fan was increased in width to increase the cooling airflow from around 22cf/sec to 25cf/sec. The combined power requirement went up to around 6hp - too much for the thin genny belt. So VW supplied a 10.2mm belt. Since this wider belt rides a little higher in the groove in the engine pulley, the belt length was increased to 912mm. So the Alt equiped cars use a 912 x 10.2mm belt.
If you use the thinner belt on an alternator equiped car it won't last nearly as long as it should.
And as one of the other posts said, make sure ALL the shims in the gen/alt pulley are in the stack - either between the pulley halves to adjust the belt tension, or under the dished nut on the outside of the rearmost pulley half.
Any chance the doghouse fan shroud has been installed incorrectly so the alt pulley position doesn't line up with the engine pulley?
The correct pulley tension is when the belt can be pushed in about 1/2inch between the pulleys. Making it any tighter than this increases the wear on the gen/alt bearings.
_________________
Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com |
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