Alternator Belt 993 C4

[citychap26]

Hi All,

Firstly Happy New Year!

Had an issue last week, my alternator belt was making loads of noise, I thought it was just because it had been raining loads, but it ended up snapping. Car went to my independent garage, they did an excellent job and got the car back to me in couple of days.

Annoyingly a couple of days ago I could smell burning, same noise and a load of smoke came into the cabin via the vents, and yes the belt snapped again, I heard it this time.

The noise was more audible when I put more load on the alternator, switch on heating and headlights.

Could the possible issue be the alternator bearing? I noticed that on the new belt a fair chunk of the teeth had been removed.

Cheers

Sunil

[paua]

Insist on genuine Porsche belts for your 993. Non-genuine belts have been known to fail. Read similar advice (may have been on Rennlist?). Replaced mine with genuine parts.

[BertBert]

Well you certainly need to investigate the cause. Might just be two failed belts but if get it checked out in case there is another issue.

[Wozy68]

BertBert said:

Well you certainly need to investigate the cause. Might just be two failed belts but if get it checked out in case there is another issue.

This ^^^^

However I also had two belts go one after another on my 993. The issue can be sometimes that the belts simply haven’t been tightened up enough...... especially so on an early one as later 993s had an update to the pulley.

The third belt fitted is still going strong yet the amount of tension required to stop a belt from slipping is quite considerable and more than you’d generally expect compared to say on a belt driven machine of other sorts.

[Orangecurry]

You have three issues

1) as the lads say, is something else wrong or did the original belt just break due to age/use?

then, assuming you can get through the above,

2) getting the correct length and width belt is an art, as Porsche specified a few different ones.... it's not using a Porsche-labelled belt that will necessarily solve your problem (Porsche don't make belts), but finding the correct one.
3) putting a new one on is an art

...so by any chance do you still have the old belt? If so can you read any of the markings?

Edited by Orangecurry on Saturday 2nd January 16:28

[Orangecurry]

This is just going to confuse you, but

I've just looked-up when I changed all of mine in 2014 (as one was starting to crack and had been trashed by the stupid wheelie-sensor) and have also popped outside to look.

My originals were - inner belt 999.192.338.50
and outer 999.192.343.50
I think the AC belt was a 13x1085

From memory, there are mostly 9.5mm and a couple of 10mm width belts that might come-up as being 'correct', but this may be the issue... I don't think 10mm belts are correct. Lengths are 776 or 760?

I bought a genuine replacement 999.192.343.50 which was 10x760 and it felt all wrong on the pulley - too tight. Some places list this belt as a 9.5.... arrrrrgh!

Remember that whoever put the previous belts on faced the same issue... but if the belt you had has lasted, it can't be 'wrong'.

Do you have AC? Which pulley version is yours? Even if you ask Porsche using your VIN, and/or look up belt-choice using the power of the interweb for good, doesn't always seem to give the correct answer. My OPC couldn't. So I bought a few.

In the end I put two Dayco 999.192.338.50 which were 9.5x776 on the inner and the outer in 2014, and all good since... but fitment is an art, with the different shims.. look up the Pelican how-to, as it addresses the fact that the belts have changed depending on engine/pulley type...or can be different - the Rennlist article doesn't mention what belt to fit at all

https://www.pelicanparts.com/techarticles/pcar_com...

ETA this excellent article only lists the belts as 9.5mm... but modern Porsche belts with the correct part number show up on the internet as 10mm

Edited by Orangecurry on Saturday 2nd January 16:18

[ThirstyMoose]

My 993 Turbo had a penchant for eating belts. Fitted the later style ‘upgraded’ pulley wheel and its been fine since.

[ThirstyMoose]

Some info here:

https://www.pelicanparts.com/techarticles/Porsche-...

[Orangecurry]

Apologies - too many words in my ramblings above - here is the management summary:

1 - is the alternator ok, or is it causing the belt to snap?
2 - if ok, and your garage have fitted a 'correct' belt, even one that has the part number of the belt that originally failed, and the new belt was 10mm instead of 9.5mm, I think there is a high chance that a 10mm would get caught in the pulley and get most of the teeth ripped out.

Another simple possibility is, even if identical, the nice new belt would be shorter than the old stretched belt, and so did they need to make adjustments when refitting.....?

Just my experience - I ain't claiming no big facts here but I'll put a pint on the replacement that broke was a 10mm belt?

(ediited for clarity)

Edited by Orangecurry on Saturday 2nd January 22:38

[citychap26]

Morning all,

So my independent is a Porsche specialist. I have a vague memory of the correct number being stamped on the new belt.

I will speak to them this morning and see what they say.

Cheers

Sinil

[Orangecurry]

If they are a Specialist, or in fact any garage, I'd hope they'd have tested the alternator to see if it was 'grabbing' or grinding or whatever before fitting a new belt?

I appreciate they did it for you 'fast' in the 'holidays' week, but even so

[Orangecurry]

The belts quite often have the width and length printed on them, in addition to any part number.

Edited by Orangecurry on Monday 4th January 11:53

[citychap26]

Hi All,

So the source of the problem has been identified. It would appear that the pulley get stuck intermittently.

I’ve been advised that there is a hairline crack in the fan so I need a new one at the cost of £400+ is this common?

The pulley is pretty expensive also at £250.

Cost of all parts is circa £900. Ouch! Plus labour also.

Cheers

Sunil

[citychap26]

Oh one thing to add, everyone who has recently been involved with my pride and joy had said it’s one of the better ones around.

I have to also say it’s an absolute pleasure to drive. It looks amazing and sounds even better 😁. Rock on 993!!

Cheers

Sunil

[ras62]

There is no such part as a pulley. It is a series of pulley half's and shims. There are also different belt lengths for various years so worth checking your vin with Porsche to be certain which one is required for your motor.
Its likely the pulley bearing(wheel hub) is worn, although pulley half's can pit and chew up belts. As for the hairline crack, it can happen but this is nothing to do with the issue at hand other than the fan must be removed to change the wheel hub. They need to determine why the pulley isn't spinning free.

[citychap26]

Hi Ras,

I didn’t go into detail, yes there are several ‘sub’ pulleys and other things.

Cheers

Sunil

[Orangecurry]

ras62 said:

They need to determine why the pulley isn't spinning free.

This.

Your garage does seem to be a typical 'change everything for new until the problem goes away' approach, which is unfortunate.

If I were you, I would go and see all of the alleged parts that need replacing.

[ras62]

I maybe quite wrong but if the garage have had a bad experience in the past when removing the bearing from the fan (fan is magnesium) then perhaps they are wanting a simple life and saying fit a new fan and bearing etc.

[citychap26]

Morning All,

So car came back yesterday, I was sitting In the lounge and heard it coming up the road .

Firstly it looked stunning as it had been washed...

The following was changed:
1, (x2) V-belt pulley half
2. Drive belt 9.5 * 776
3. (X2) V-belt pulley half
4. Fan wheel
5. Pulley
6.Drive belt AV 13x1085.

Okay so I took the car for a quick drive.... It was very different. I’ll list my observations:
1, The steering felt different, not sure it’s connected to work done.
2. There was a sound which became louder as the revs increased, I can only describe it as this ( it sound like a Red Indian yodelling). Please I’m not being racist, it’s the only way to explain the noise.
3. The car was sliding around, road was rather wet.
4. The clutch felt different also.

I think that the new fan wheel is lighter than the old one, perhaps that is making the car feel different?

Now I love my Porsche Independent, they have looked after all of my pervious cars. They said to put some miles on it and see if things settle. Bear in mind my car has done 115k miles. The engine is sound.

Any thoughts chaps?

Cheers

Sunil

[Orangecurry]

You do get up early don't you.

Are you sure it is your car they brought back?

Errrrm all I can think is that you've got some new vibration coming through that is making the car feel different.... but

ETA I would park up with the engine lid open, and ask someone to gently increase the revs whilst you watch the fan. Stand well back

Can you see any movement (other than rotational) or deduce where the noise is located, if it happens?

I've only read one thread where someone was asking about different fans, materials and weights, and that was on Rennlist, and I'm not sure they thought fans were 'different' by design, but recent manufacture might not be the same as original. I'll see if I can find it. (ignore that - it was the fan housing they were talking about.)

Why do you think the new fan is lighter - did the Indy weigh old vs new. I hope you've kept the old one - please weigh it

Edited by Orangecurry on Friday 15th January 10:41