Porsche 993 DIY
Discussion
Anyone changed the V belts on their 993?
I was driving along with Wheeljack88 in the passenger seat- trying to compete with the noise of his Chim, but failing abysmally :D (but perhaps surpassing his traction in the treahorous wet conditions!).
Anyway, there was a little knock noise and the generator light came on, and after a while- so did the ABD and ABS warning lights.
I realised that my alternator V belt must have come off, and there wasn't enough electrical power in the car to keep the braking system pressurised...
Anyway back at base after surfing the web and consulting my factory manual I realise that the V belt change isn't QUITE as straight forward as initially thought.[The belt had snapped due to wear and old age- apparently]
Shims are used to tension the belt- and not a tensioning strap as on , say, an old Bimmer. Porsche reccommends the use of a V belt tension measuring gauge. The other special tool they reccommend is tool# 999 571 052 02 which will hold the alternator shaft while you loosen the shaft bolt.
This excellent website outlines some of it
http://p-car.com/diy/vbelt/
The other thing of note to 993tt owners is that the belt may have snapped due to a design flaw:
Apparently there is an alternator pulley update kit availiable- with a larger diameter pulley. If you alternator V belt has 9.5 X 753 on it- it is likely to be fitted with the update kit. If it has 9.5 X 757 sixe belt it has the old style belt. There was just enough belt left in my engine bay to make out a "757" measurement. Apparently the update kit is there to prevent premature wear of the belt. Certainly of all the old cars I've owned, neglected and otherwise, I've had squealing belts but never had a belt snap on me. From my experience in engine design I know there are minimum radius pulley guidelines set to ensure belt life longevity.
I hope changing the belt is straight forward. Has anyone on here tackled the change without using the special tools? Anything to watch for?
I was driving along with Wheeljack88 in the passenger seat- trying to compete with the noise of his Chim, but failing abysmally :D (but perhaps surpassing his traction in the treahorous wet conditions!).
Anyway, there was a little knock noise and the generator light came on, and after a while- so did the ABD and ABS warning lights.
I realised that my alternator V belt must have come off, and there wasn't enough electrical power in the car to keep the braking system pressurised...
Anyway back at base after surfing the web and consulting my factory manual I realise that the V belt change isn't QUITE as straight forward as initially thought.[The belt had snapped due to wear and old age- apparently]
Shims are used to tension the belt- and not a tensioning strap as on , say, an old Bimmer. Porsche reccommends the use of a V belt tension measuring gauge. The other special tool they reccommend is tool# 999 571 052 02 which will hold the alternator shaft while you loosen the shaft bolt.
This excellent website outlines some of it
http://p-car.com/diy/vbelt/
The other thing of note to 993tt owners is that the belt may have snapped due to a design flaw:
Apparently there is an alternator pulley update kit availiable- with a larger diameter pulley. If you alternator V belt has 9.5 X 753 on it- it is likely to be fitted with the update kit. If it has 9.5 X 757 sixe belt it has the old style belt. There was just enough belt left in my engine bay to make out a "757" measurement. Apparently the update kit is there to prevent premature wear of the belt. Certainly of all the old cars I've owned, neglected and otherwise, I've had squealing belts but never had a belt snap on me. From my experience in engine design I know there are minimum radius pulley guidelines set to ensure belt life longevity.
I hope changing the belt is straight forward. Has anyone on here tackled the change without using the special tools? Anything to watch for?
I think the shimming arrangement is the same (or similar) on earlier (930) 911's.
I changed mine on the 3.2C, and had no problems at all, all you need is the special spanner to undo the nut.
I know that some of the later 911's have two belts, one for the fan, and one for the alternator, to get optimum speed for both. That could make it trikier.
I just did the tension the same way as for a standard arrangement, on the basis of nust about being able to deflect the belt with the middle finger.
The only disadvantage is that the range of adjustment is not great. You do have to have the right belt for the job.
Edited to add;
Make sure you keep all the shims on the spindle. They'll only get lost otherwise. The ones that don't get used go outside of the pulley halves (obviously).
Further edited to add;
The special spanner should be in the car's factory toolkit, with the jack and such.
>> Edited by dilbert on Sunday 14th August 17:03
I changed mine on the 3.2C, and had no problems at all, all you need is the special spanner to undo the nut.
I know that some of the later 911's have two belts, one for the fan, and one for the alternator, to get optimum speed for both. That could make it trikier.
I just did the tension the same way as for a standard arrangement, on the basis of nust about being able to deflect the belt with the middle finger.
The only disadvantage is that the range of adjustment is not great. You do have to have the right belt for the job.
Edited to add;
Make sure you keep all the shims on the spindle. They'll only get lost otherwise. The ones that don't get used go outside of the pulley halves (obviously).
Further edited to add;
The special spanner should be in the car's factory toolkit, with the jack and such.
>> Edited by dilbert on Sunday 14th August 17:03
I had a similar experience late last year but was lucky enough to have the alternator belt take the AC belt with it as well.
I would suggest buying your belts from an OPC and make sure they're exactly the same size as the one you're taking off.
I'm not convinced that the P Car DIY is correct with regard to listing the alt belt size that corresponds to the pulley update kit for a 993tt. I fitted a 9.5 by 757 belt to my 97 993tt as that's what was there.
The Porsche 12 point tool mentioned on the p-car DIY won't work on a 993tt as there isn't enough room between the end of the alternator shaft and the sheet metal at the back of the engine. I ended up buying a 10 mm triple square bit from my local Snap-On man and had to shorten it in order to get it to fit. Get the one you put a spanner or socket on, not the one that fits in a 3/8" ratchet.
The nut on the alternator shaft was v v tight. I ended up bending two 11 mm spanners trying to hold the tri-square bit against a 24 mm spanner and bought a longer and stronger 11x13mm combination spanner from Halfords that finally did the trick.
You might as well replace the fan and AC belts as well. You'll find refitting the fan belt to be an absolute b*gger of a job. There's very little clearance between the pulley flange and the sheet metal at the back of the car. It may help to put a jack under the engine to lift it up a bit; I only thought of that after I finished the job.
Good luck! Send me an email if I can help further.
>> Edited by phelix on Sunday 14th August 19:12
I would suggest buying your belts from an OPC and make sure they're exactly the same size as the one you're taking off.
I'm not convinced that the P Car DIY is correct with regard to listing the alt belt size that corresponds to the pulley update kit for a 993tt. I fitted a 9.5 by 757 belt to my 97 993tt as that's what was there.
The Porsche 12 point tool mentioned on the p-car DIY won't work on a 993tt as there isn't enough room between the end of the alternator shaft and the sheet metal at the back of the engine. I ended up buying a 10 mm triple square bit from my local Snap-On man and had to shorten it in order to get it to fit. Get the one you put a spanner or socket on, not the one that fits in a 3/8" ratchet.
The nut on the alternator shaft was v v tight. I ended up bending two 11 mm spanners trying to hold the tri-square bit against a 24 mm spanner and bought a longer and stronger 11x13mm combination spanner from Halfords that finally did the trick.
You might as well replace the fan and AC belts as well. You'll find refitting the fan belt to be an absolute b*gger of a job. There's very little clearance between the pulley flange and the sheet metal at the back of the car. It may help to put a jack under the engine to lift it up a bit; I only thought of that after I finished the job.
Good luck! Send me an email if I can help further.
>> Edited by phelix on Sunday 14th August 19:12
phelix said:
I had a similar experience late last year but was lucky enough to have the alternator belt take the AC belt with it as well.
I would suggest buying your belts from an OPC and make sure they're exactly the same size as the one you're taking off.
I'm not convinced that the P Car DIY is correct with regard to listing the alt belt size that corresponds to the pulley update kit for a 993tt. I fitted a 9.5 by 757 belt to my 97 993tt as that's what was there.
The Porsche 12 point tool mentioned on the p-car DIY won't work on a 993tt as there isn't enough room between the end of the alternator shaft and the sheet metal at the back of the engine. I ended up buying a 10 mm triple square bit from my local Snap-On man and had to shorten it in order to get it to fit. Get the one you put a spanner or socket on, not the one that fits in a 3/8" ratchet.
The nut on the alternator shaft was v v tight. I ended up bending two 11 mm spanners trying to hold the tri-square bit against a 24 mm spanner and bought a longer and stronger 11x13mm combination spanner from Halfords that finally did the trick.
You might as well replace the fan and AC belts as well. You'll find refitting the fan belt to be an absolute b*gger of a job. There's very little clearance between the pulley flange and the sheet metal at the back of the car. It may help to put a jack under the engine to lift it up a bit; I only thought of that after I finished the job.
Good luck! Send me an email if I can help further.
>> Edited by phelix on Sunday 14th August 19:12
Thanks Phelix for the words of advice.
I only JUST received all the parts in the post today would you believe?
I HAVE managed to USE the 12 point Porsche tool. I DID find it very tight- to fit on the end of the shaft- but managed it, I wedged it against the inner metal bumper- and put an old brake pad (a rear one from an Alfa 75
)between the tool and the inner bumper. I then got the bolt off-although it was very tight. So I've tackled one of the worse jobs, it sounds like I have the fan belt fitting to look forward to- but I'll take your advice and jack the car up.
I'm dead busy this weekend- going off to Germany, so I'll probably procastinate and not tackle this job until I get back next week.
BTW- to all those who said the 12 point tool was in the tool kit, it isn't on the 993tt- perhaps it is on earlier models?
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