balanceshaft belt

[DSyko]

First of all, hi to everyone this is my first post.
I have a porsche 944 16v ventiler and love it.
The previous owner told me that they had had the belts changed about a year ago but i decided to check the condition anyway and found that the balanceshaft belt was extremely slack! Is this correct? as finding the belt this slack has caused me concern and do not want to drive it untill i get info on this matter.
Please help as i love this thing.

 

[PSH]

what you call slack is probably ok... they have more movement in them than most may realise... so i bet it's ok but if worried get it checked of course

Oh.. and hi and welcome...[8D]

Pete

 

[sawood12]

Welcome. The process when belts have been replaced is to re-check the tension after 1000km and re-tension if required. If you are not 100% sure the previous owner adhered to this then if I were you 'd get them checked out. Better to be safe than sorry. In theory a balance shaft belt failure is a safe failure, but in reality there is a chance it can take out your timing belt.

 

[944 man]

ORIGINAL: sc0tty

There are a lot rumours and myths generated on internet forums...

Yes, there is a lot of faux knowledge; that in reality is little more than repeated tittle-tattle. If your car has a proper service history though, youll see that this isnt a myth: Porsche clearly state that the belts need to be checked after 2,000 - 2,500 miles and youll see this written on the yellow 'toothed belt replacement' yellow card.

Simon

 

[PSH]

Yes, there is a lot of faux knowledge; that in reality is little more than repeated tittle-tattle. If your car has a proper service history though, youll see that this isnt a myth: Porsche clearly state that the belts need to be checked after 2,000 - 2,500 miles and youll see this written on the yellow 'toothed belt replacement' yellow card.

This is true simon and yes they will say so for a reason, however they also say to tension the timing belt to IIRC 3.5 on their little tool. Many years ago I phoned a very well known Porsche specialist to ask what this was in english, ie something any normal belt tensioning tool can read. I was told and quote , don't bother with that, we only check that it has around 10mm movement on it's longest stretch which kind of surprised me. Having said that my belts have been changed at least 5 times in the last 8 years and I use the old fashioned method now of a 1/4 turn is good enough. Hope i havn't tempted fate as I havn't changed them in two years which is very long for me , very long indeed..lol


Pete.....[8D]

 

[PSH]

Crikey, 5 times on 8 years, you obviously change them yourself then? Every 4 years is the norm I thought.

Yes Scotty.. i get a little paranoid over belts......[]

 

[retroreject]

Getting mine done this friday..as a precaution. Owner advised me, as it's been 4 years and many miles since they were last done. My steering rack also needs replacing. Ho hum

 

[sawood12]

ORIGINAL: sc0tty

I don't neccesarily believe this retensioning requirement, I had all my belts replaced, and they are still tensioned correctly. The hydraulic spring tensioner has to be set at the time of the cam belt change on the S2, so why would it need to be retensioned? Plus, my specialist mechanic is factory trained, worked for Porsche GB for 20 years and has run his own porsche specialist garage for many more years, and has changed more cambelts than I have had hot dinners. I know who I trust. There are a lot rumours and myths generated on internet forums...

Just my opinion of course...[]

I'd check out yor specialists credentials as on the face of it he doesn't appear to be Porsche traied at all as Porsche train their mechanic to tension belts in accordance with their own manual. Either way it is bad advice. For a start, not all 944's have hydraulic spring tensioners and in any case the tensioners are not there to primarily tension the belt - just to maintain tension when the belt waggles around under use.

And when I had my belt tensioned last time around a retention was required after a check.

Of course with any car you can tension the belt via some arbitrary rule about 10mm displacement or twisting the belt through 90 degrees. But what does it mean? 10mm displacement at what force? Twisting the belt through 90 degrees at what force? These methods will produce a huge scatter as to the actual tension of the belt and at best if a specialist has got away with it to now they've been lucky. If you want to do it properly then use the correct tool. If you want to do it another way and ride your luck (or someone elses) then that's not doing the job properly. You wouldn't believe your specialist if he was doing a head job and told you that he ignores the torquing sequence of the head bolts no matter if he was Porsche trained or not - same principle here.

 

[DSyko]

ok thanks for the replys. Think i will get an expert opinion on this as dont really want to kill the engine to soon.
There is one idler pulley doing nothing in there, ie no belt contact to it at all!?! now that can never be right, can it???
Oh the joys of motoring.

 

[andy watson]

Hi,

Another item you might like to get checked out would be the cam chain slipper, not listed on Porsche service schedule but needs to be done.

I speak fron experience, belts have always been changed as the service history confirms but no indication of the slipper being changed.

Replacement engine required after plastic slipper broke and consquently ended up with smashed cyclinder head!!

Andy

 

[tref]

Yes, it is correct - that is an "anti-whip pulley". From what you have described, it sounds like your belts are set about right. The balance shaft belt should be what seems very loose.

The club has the correct tool for measuring the belt tension available for hire... why worry?

Now I know many people get away with it... but I sat at a bar once with a 944 turbo owner who told me the old 1/4turn trick was fine and all the tensioning procedures where unnecessary... later in the same conversation he told me how he had a belt snap and had to replace a couple of valves....

 

[rcsalmons]

ORIGINAL: sawood12

ORIGINAL: sc0tty

I don't neccesarily believe this retensioning requirement, I had all my belts replaced, and they are still tensioned correctly. The hydraulic spring tensioner has to be set at the time of the cam belt change on the S2, so why would it need to be retensioned? Plus, my specialist mechanic is factory trained, worked for Porsche GB for 20 years and has run his own porsche specialist garage for many more years, and has changed more cambelts than I have had hot dinners. I know who I trust. There are a lot rumours and myths generated on internet forums...

Just my opinion of course...[]

I'd check out yor specialists credentials as on the face of it he doesn't appear to be Porsche traied at all as Porsche train their mechanic to tension belts in accordance with their own manual. Either way it is bad advice. For a start, not all 944's have hydraulic spring tensioners and in any case the tensioners are not there to primarily tension the belt - just to maintain tension when the belt waggles around under use.

And when I had my belt tensioned last time around a retention was required after a check.

Of course with any car you can tension the belt via some arbitrary rule about 10mm displacement or twisting the belt through 90 degrees. But what does it mean? 10mm displacement at what force? Twisting the belt through 90 degrees at what force? These methods will produce a huge scatter as to the actual tension of the belt and at best if a specialist has got away with it to now they've been lucky. If you want to do it properly then use the correct tool. If you want to do it another way and ride your luck (or someone elses) then that's not doing the job properly. You wouldn't believe your specialist if he was doing a head job and told you that he ignores the torquing sequence of the head bolts no matter if he was Porsche trained or not - same principle here.

No 944's have "hydraulic" spring tensioners they have a spring only and this will not maintain tension when the belt waggles as the tensioner is bolted in position once the tension is set.

Cheers

Rich.

 

[pauljmcnulty]

The club has the correct tool for measuring the belt tension available for hire... why worry?

Exactly. Although, you only pay the postage cost (if you can't pick it up), so really it's free. Add that into free insurance valuations as another under-used Member benefit. []

As the Club have two, perhaps it's worth me keeping one myself and then it could be picked up, or used, at events I attend?

James, does your mechanic offer a full warranty on the belts even though he tensions them by hand? I'm sure he is perfectly capable of judging it very well, but why would he risk it? Does he not bother with a torque wrench when fitting the wheels? Or use the dipstick to check the oil level? Does he inflate the tyres by eye? I can't see the point of not doing it properly, as he must have the tensioning tool sitting there slowly rusting away. [8|]

 

[ChasR]

I'll get the tensioning tool eventually via membership but first, but all of my cash is going towards another S2 engine, and my dad's daily's engine is playing up too (Valve seat recession on a HUUUUUuuge scale (Seats are buried deep in the head) hence reprioritising the budgets (The Mondeo V6 engine change makes the Porker look cheap in comparison).

Some people get all the luck eh LOL?

 

[Hilux]

Every 4 years is the norm I thought.

Rubber composite belts have a shelf life. Unlike chains they decay and stress fracture so I`d personally err on the side of caution so if Porsche say 4 years I`d do it every three.

As for belt tension, I am perfectly happy with the 90 degree rule, if the belt loses tension at all then it can jump a tooth or teeth however if it is running around a tensioner and hasnt stretched or is worn then the likely hood of it jumping a cog is small. Consider a belt under some tension and then imagine how far it has to go to stretch and jump teeth. Where it pulls the belt it is in tension and where pushed is where it will jump but only if very slack.

If you really take time to study the issues and actually get a belt in your hands and see how inert it is then you`ll realise that its 100 times more likely belt or tensioner failure that will destroy an engine, not the fact that the belt is a slightly slack.

 

[ChasR]

One very well renowned specialist said to me on low mileage cars, 5 years is fine, but no more than 40,000 miles. He said the belts generally last, but the rollers don't.

 

[tref]

ORIGINAL: Hilux

Every 4 years is the norm I thought.

Rubber composite belts have a shelf life. Unlike chains they decay and stress fracture so I`d personally err on the side of caution so if Porsche say 4 years I`d do it every three.

As for belt tension, I am perfectly happy with the 90 degree rule, if the belt loses tension at all then it can jump a tooth or teeth however if it is running around a tensioner and hasnt stretched or is worn then the likely hood of it jumping a cog is small. Consider a belt under some tension and then imagine how far it has to go to stretch and jump teeth. Where it pulls the belt it is in tension and where pushed is where it will jump but only if very slack.

If you really take time to study the issues and actually get a belt in your hands and see how inert it is then you`ll realise that its 100 times more likely belt or tensioner failure that will destroy an engine, not the fact that the belt is a slightly slack.

Agree, with a couple of Caveats... one is over tensioning knocking out bearings. Secondly is the belt doesn't need to "stretch" a full tooth, it needs to stretch just enough to allow the belt to "ride up" over the teeth... this appears to take considerably less stretching... I have played about with sticking a spanner on the spanner on a crank and seeing how the belt behaves at low speed. I also have a vague recolection of changing the belts once and getting it one tooth out...and finding out by the engine "locking" whilst doing the "two revolution check everything is free" after the job was complete. This suggests that one tooth out is enough to cause engine damage. Though time clouds the memory on this one...

Regarding the "retensioning", I believed it was a "tension check", only retensioning if necessary... which I would suggests makes more sense. The acceptable range is different to account for it bedding in.

 

[Hilux]

Secondly is the belt doesn't need to "stretch" a full tooth, it needs to stretch just enough to allow the belt to "ride up" over the teeth... this appears to take considerably less stretching...

Without appearing to nit pick I didnt actually say that `stretch` makes it jump teeth, I said its when it loses tension.

if the belt loses tension at all then it can jump a tooth or teeth however if it is running around a tensioner and hasnt stretched or is worn then the likely hood of it jumping a cog is small.

Its unlikely a belt will stretch anyway, its the lack of tension that allows sufficient slack for a belt to jump hence my last sentence in the post.

you`ll realise that its 100 times more likely belt or tensioner failure that will destroy an engine, not the fact that the belt is a slightly slack.

 

[sawood12]

ORIGINAL: ChasR

One very well renowned specialist said to me on low mileage cars, 5 years is fine, but no more than 40,000 miles. He said the belts generally last, but the rollers don't.

I just don't see any point in not adhering to the recommended schedule. What is there to gain? Decent specialists will (should) recheck your belt tension and re-adjust for free (mine does) so why wouldn't you do this? The mileage and time limits are there fore very good reasons - mileage limit is there as over use the internal chords frey and weaken (the strength of the belt is in the chords and not the rubber). The time limit is there to prevent breakdown of the rubber through chemical and ozone attack as natural rubber basically is degraded over time when exposed to air causing it to harden and crack.