tensioning my alternator drive belt

[bibble]

Hello to all, probably a subject that has been discussed in the past but rapidly getting to my wits end..... My 83 SC alternator failed around a week ago. Had the original unit repaired -great.

Re-installed it, but can I get the belt tight? I can get the car running ok, alternator warning light off, but the belt is still loose and heats up pretty quickly (as does the pulley) and unpleasant smell comes from the belt. Prior to being taken out there were three shims either side, i have tried every combination known to man i think in terms of 4 on this side two on the other etc etc to get it to tighten up. The difference however appears negligible wherever the shims are, the only difference is the angle between the pulley and the crank pulley. I have checked the alternator is sitting in the fan housing correctly, tried to ensure the whole fan and alternator assembly are correctly located before doing the shims bit, and i am fairly sure it is all back as it should be but!!!!!

I am not sure how the system actually works either really, in that you are able to put three shims on the alternator side, hook the pulley into the belt whilst its attached to the crank, without much effort then put the pulley on to the end of the alternator, then stick the next three shims inside and put the cone washer on, nut and then crack it up pretty tight and its still loose! At what point do you get some tension. Or am i doing something wrong????

Any help - advice greatly appreciated, unless anyone wants to buy a very cheap SC cab after i have set fire to t!

Best wishes

Jonathan

 

[bones]

Hi Jonathan, Some shims fit behind the pulley, the more shims you fit the slacker the belt will be as the belt will ride lower on the pulley, the tightest fitting is obviously, no shims. The remaining spare shims are put on the other side of the pulley between cone washer and pulley which you seem to have installed corrctly. Have you changed the belt? There are different sizes, if it's an old belt it may have come to the end of its life, perhaps you need a new one?

 

[bibble]

Hello Bones, thanks for the reply! Yes I changed the belt, the one that came off was only about a year old (replaced by the AA) I compared it with the old and it was very similar in terms of length etc. The system itself just seems a little strange as I said I am used to being able to move the alterantor around an arc, that tensions the belt on my previous cars, this pulley-shim system doesn't seem to make any sense to me, in terms of at waht point do you pull the alternator away from the crank and get some ension into the belt. Thats where I am concerned have I put the alternator badck on to the fan housinm correctly, have I fitted the fan/alternator assembly correctly into the car, but I can't see how I could have got it so wrong that the alternator will still fit etc but that it won't tension! Bah humbug!!!! Jonathan

 

[nathan 1981 930 G50]

The shim system is excellent, providing you have the correct size belt. Buy a genuine belt from your local OPC and follow Bones' instructions.

 

[bones]

Nathan's spot on buy a GENUINE belt from an OPC and a spare to keep in the car. Buy some spare shims too. Sounds to me there is something not right with the belt or you have too many spacers behind the pulley, try no shims and see how you get on, if it's impossible to fit add one shim at a time until it fits. When you get a result start the engine and recheck to see if it has slipped at all and the retaining nut is still tight. Check again after a few days use. Other people sell belts http://www.type911shop.co.uk/shop/article_2286/911-Fan-Belt-1965-75-_-1979-89.html?shop_param=cid%3D1%26aid%3D2286%26 but go OPC for this item.

 

[bibble]

Thanks to all for the contribution, and I cannot believe what I did. Checking the net today I came across an article that shows the pulley assembly without the aircondition pulley on the end and realised that although I have the pump etc on the car(it has never had the belt on since I bought the car) that I was putting the belt onto that pulley rather than behind it and into the correct position - what a muppet! Too busy when I strpped it down thinking about wiring it back uo correctly and didnt take notice of this fundamental fact! A lesson learned and rather than hide my error thought it wise to share just in case anyone else is daft enough to do the same..... Best wishes Jonathan

 

[chris.hevey]

Yes but what's the saying? "Better to have tried and failed than stayed in bed all day" or something? (Bones, Do you do any of those Cistficates of Muppetry left? [])

 

[bones]

ORIGINAL: chris.hevey Yes but what's the saying?  "Better to have tried and failed than stayed in bed all day" or something? (Bones, Do you do any of those Cistficates of Muppetry left? [])

You're so cruel Chris! but.......[][][]

 

[bibble]

Thanks chaps for your kind encouraging words......! Take it easy JM

 

[nathan 1981 930 G50]

Glad you got it sorted but after 10 years of 911 ownership I can assure you that genuine parts are the way to go, why fit lower quality parts and spoil a high quality car. Of course the exception to the rule is some more modern performance parts, you can always ask on these boards for opinions about any.

 

[bibble]

Agreed Nathan, I have used Porsche parts on the 911 (as I also did for my 944s which sadly left my care a couple of months ago) i have replaced the blower, Clutch, gearlinkageetc as the quality of them is good, prices are reasonable in the main and it keeps originality which whilst not being totally everything to me, is important when you can. I have used other after market bits though for example a new roof from Forest Fine after a kind person slashed the roof in Devon a couple of years back. With the alternator I wanted to keep the original unit as the bearings and general condition were good, and just needed the electrical internals re-furbished. Thanks for the note JM

 

[alan_o]

The alternator belt on my SC (79 Model) give way last night. I thought I had a spare, but alas not[]

Now when I went to order a new one I see there are 2 sizes to choose from: PN 999-192-097-50 - Narrow v-belt - 9.5 x 725 79-SC

PN 999-192-176-50 - Narrow v-belt - 9.5 x 710 79-SC

Does anyone know how to check which one I would need?

If not I'll buy one of each and see which fits best.

Many thanks

Alan

 

[T911UK]

A 78 MY needs a 710

 

[hotfrog1]

According to the Porsche workshop manual the belt size was changed to 710 x 9.5 from and including 1980 models. This is the same time as the fan size was changed. However, the parts catalogue shows this change was made during model year 1979.

In my limited experience these belts are rapidly destroyed when any slipping occurs and they tend to become slightly elastic. A new genuine belt would help, or at least eliminate it.

 

[hotfrog1]

Had a further look and the attached snip from the parts catalogue shows the engine number change[attachment=Capture2.PNG] point.