timing belts
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Frenchy
New member
Buy them from Opc and they cost a fair bit, buy from an independent parts outlet a 3rd of the price and the same things in a different box if you specify Gates (they also make hunter wellies)
Porsche tax applied big style, rotor arm from Porsche circa £52 from a well known independent in a Bosch box £17.
Porsche tax applied big style, rotor arm from Porsche circa £52 from a well known independent in a Bosch box £17.
Thanks for the comments guy's, yeah I wasn't sure you could retro fit a spring tensioner. I've been happily using the eccentric roller for over 15 years now so I'll be happy to stick with it I think. Reason for the question is the car has covered about 6k miles since the last belt change 4-5 years ago and when I checked tension a few weeks ago noticed the balance belt had worn teeth, and the cam belt needed to be tensioned a bit and was hitting the limit on the tensioner. They are both conti belts at the moment.
Note, I set my own tension by feel not with the tool, and from experience I use slightly less tension than the tool would apply so I was surprised the belt had stretched as much as it had.
I've only found gates belts via ebay so far. Any recommendations on stockists?
Note, I set my own tension by feel not with the tool, and from experience I use slightly less tension than the tool would apply so I was surprised the belt had stretched as much as it had.
I've only found gates belts via ebay so far. Any recommendations on stockists?
PSH
PCGB Member
Hi Phil
Here's a link to Gates.. http://www.gates.com/products/automotive/passenger-car-and-light-truck/timing-system/timing-belt-component-kits-with-water-pump They do list some suppliers although I suspect they are all US based, I'm not sure where my son gets his, I know he has to order them in....I'll try to remember to ask him next time he's over..
cheers
Pete
Here's a link to Gates.. http://www.gates.com/products/automotive/passenger-car-and-light-truck/timing-system/timing-belt-component-kits-with-water-pump They do list some suppliers although I suspect they are all US based, I'm not sure where my son gets his, I know he has to order them in....I'll try to remember to ask him next time he's over..
cheers
Pete
blade7
Well-known member
PhilKent said:
Likewise, I set the timing belt tension so the water pump pulley can just be turned by a strong hand against the belt on a cold engine. Belt tech has improved in the 30 + years since the 944 came out. I don't bother replacing belts and tensioners every 4 years on low mileage use. I do check the tension occasionally though.
That's brave - the accepted wisdom on here is that more than four years is running your luck. There are apparently heard a number of stories of people whose belts have let go soon after the 4 year mark (although I'm not sure I have heard any first-hand).blade7 said:
Mind you, it's always struck me that changing the tensioners every time is overkill. The bearings on the ones that I have taken out over the years have always been entirely fine - to the extent that a friend who helped me with them once laughed at me for spending the money on them. I guess it all comes down to how lucky you feel, and new belts and tensioners are (comparatively) cheap insurance against and expensive rebuild.
Oli.
blade7
Well-known member
I'm fairly confident it's usually an outside force that damages a correctly tensioned, dry, belt that's say under 6 years/25k old. That and when you do the belts yourself you can have an ear for an unusual noise. Like you say though tensioners are relatively cheap and if there was a hint of drag or noise I'd change them all irrespective of use. I only do about 3k of longish drives a year in my car, if it was 2 or 3 times that of stop start driving it may be different.
Touches wood [
].
Touches wood [
].
Indi9xx
New member
From training and education.
What destroys a belt?
From education training and experience
* Entropy (Everything wants to return to its original component materials) - Very slow
* Oxygen (Oxidises the rubber from the outside inwards, forming cracks eventually, which then allow more oxygen deeper into the belt)
* Wear (Accelerated if the tension is too high or too low)
* Incorrect installation
Who makes the belts for Porsche?
Over the years I have seen the following belts in Genuine Porsche boxes.
* Dayco
* Gates
* Bosch
* Continental
How long can an incorrectly setup or installed belt last?
* As little as a few seconds
* As long as a correctly installed belt
Depends on how incorrectly it has been installed or setup (I have seen many weird things going on in 944 belt covers)
What else accelerates belt degradation?
* Contamination from oil
* Contamination from power steering fluid
* Contamination from coolant
* Contamination from dirt/grit
* Contamination from fuel
* Contamination from plastic dressings
* Contamination from sprays such as WD40
* Ionisation of the air in the cam belt cover
How soon can a correctly tensioned good quality belt without contamination last?
* Soonest I have seen is 5 years with a missing ionisation cap.
* Soonest I have seen with no visible signs of cause - 6 years
* Oldest belt that I have seen break was 26 years old!!!
When would I change the belts on my own 944 fleet?
* Every 5 years without fail and I check inside the cover every year for contamination or issues and always check for leaks every time I drive them.
When would I recommend customers change them?
* Every 4 years (as you might not have your belt, oil seals and leaks checked so often as I do)
How much damage is caused by not changing them?
* Wrecked cylinder head (Valve contacts and bent/detaching valve heads)
* Wrecked pistons (Valve contact, sometimes with valve heads detaching and bouncing around!)
* Wrecked cylinder block (mushroomed out pistons split the bore)
Other advice.
* Change the water pump, tensioners, rollers and front engine oil seals on every second belt change. The water pump can fail through age as well as mileage, as can the seals and tensioners/rollers. Any of these parts can cause the belt to fail.
* Make sure your car has an ionisation cap between the distributor cap and upper front cam belt cover.
This is an important one.
When the 944 was designed, it had a hose that ran between the cam belt cover and air box.. This was to bring fresh air through the belt covers, and remove air which had been ionised by the electrical activity within the distributor cap. There was also a plastic cap between the distributor cap and the cam belt cover, to reduce the amount of contamination of the air within the belt cover with air ionised within the distributor cap.
In about 1988, Porsche eventually go to the bottom of why so many 944s suffered with hydrolocked engines following driving through deep puddles or crossing a river/ford crossing... It turned out that as soon as water was sprayed around the front crank pulley, or the pulley entered water, the water would go into the belt cover and the balance belt would throw this water directly at the vent port which had the hose to the air box.. Once the air box contained a certain amount of water, or you turned a corner, the water would flow through the airflow meter, and get sucked into the engine... Nasty.
Porsche then issued a TSB to say that all Porsche models should have this hose where fitted (important) and a blanking plug fitted (Not so important, I leave them open for ventilation on the advice of my mentor at Porsche).
The problem with this deleted hose, is that without it, it is even more critical to have the ionisation cap installed. They are cheap and available.
That is all
What destroys a belt?
From education training and experience
* Entropy (Everything wants to return to its original component materials) - Very slow
* Oxygen (Oxidises the rubber from the outside inwards, forming cracks eventually, which then allow more oxygen deeper into the belt)
* Wear (Accelerated if the tension is too high or too low)
* Incorrect installation
Who makes the belts for Porsche?
Over the years I have seen the following belts in Genuine Porsche boxes.
* Dayco
* Gates
* Bosch
* Continental
How long can an incorrectly setup or installed belt last?
* As little as a few seconds
* As long as a correctly installed belt
Depends on how incorrectly it has been installed or setup (I have seen many weird things going on in 944 belt covers)
What else accelerates belt degradation?
* Contamination from oil
* Contamination from power steering fluid
* Contamination from coolant
* Contamination from dirt/grit
* Contamination from fuel
* Contamination from plastic dressings
* Contamination from sprays such as WD40
* Ionisation of the air in the cam belt cover
How soon can a correctly tensioned good quality belt without contamination last?
* Soonest I have seen is 5 years with a missing ionisation cap.
* Soonest I have seen with no visible signs of cause - 6 years
* Oldest belt that I have seen break was 26 years old!!!
When would I change the belts on my own 944 fleet?
* Every 5 years without fail and I check inside the cover every year for contamination or issues and always check for leaks every time I drive them.
When would I recommend customers change them?
* Every 4 years (as you might not have your belt, oil seals and leaks checked so often as I do)
How much damage is caused by not changing them?
* Wrecked cylinder head (Valve contacts and bent/detaching valve heads)
* Wrecked pistons (Valve contact, sometimes with valve heads detaching and bouncing around!)
* Wrecked cylinder block (mushroomed out pistons split the bore)
Other advice.
* Change the water pump, tensioners, rollers and front engine oil seals on every second belt change. The water pump can fail through age as well as mileage, as can the seals and tensioners/rollers. Any of these parts can cause the belt to fail.
* Make sure your car has an ionisation cap between the distributor cap and upper front cam belt cover.
This is an important one.
When the 944 was designed, it had a hose that ran between the cam belt cover and air box.. This was to bring fresh air through the belt covers, and remove air which had been ionised by the electrical activity within the distributor cap. There was also a plastic cap between the distributor cap and the cam belt cover, to reduce the amount of contamination of the air within the belt cover with air ionised within the distributor cap.
In about 1988, Porsche eventually go to the bottom of why so many 944s suffered with hydrolocked engines following driving through deep puddles or crossing a river/ford crossing... It turned out that as soon as water was sprayed around the front crank pulley, or the pulley entered water, the water would go into the belt cover and the balance belt would throw this water directly at the vent port which had the hose to the air box.. Once the air box contained a certain amount of water, or you turned a corner, the water would flow through the airflow meter, and get sucked into the engine... Nasty.
Porsche then issued a TSB to say that all Porsche models should have this hose where fitted (important) and a blanking plug fitted (Not so important, I leave them open for ventilation on the advice of my mentor at Porsche).
The problem with this deleted hose, is that without it, it is even more critical to have the ionisation cap installed. They are cheap and available.
That is all
blade7
Well-known member
What about the effect of setting timing belt tension on a cold engine on a used waterpump? Hardly conclusive I know, but to the best of my knowledge my water pump is at least 15years/30k old and shows no sign of leakage. I'm not advising anyone to set the cambelt tension or run the belts the way I do, that's my risk.
Indi9xx
New member
Well that is another reason for changing the water pump every other belt change.
Partly because on a second belt change the wear in the pump shaft bearing will not effect the belt tension, but also because often not long after putting a fresh belt with the correct tension onto a third belt often will mean that the water pump will not last as long as that third belt will, making not changing the pump on the second belt a false economy.
Partly because on a second belt change the wear in the pump shaft bearing will not effect the belt tension, but also because often not long after putting a fresh belt with the correct tension onto a third belt often will mean that the water pump will not last as long as that third belt will, making not changing the pump on the second belt a false economy.
Very helpful reply Jon, thanks.
So for my own case I've ordered new belts and rollers, although I replaced them all only 5-6 years ago. As mentioned the cambelt was at it's adjustable limit even though it'd only covered about 5-6K in that time and the balance belt showed signs of failing teeth, so I've gone for Dayco balance belt and a Gates cambelt (the cool blue 'racing' version) to see if it will perhaps not stretch as much as the currently fitted 'Conti' belt has.
So for my own case I've ordered new belts and rollers, although I replaced them all only 5-6 years ago. As mentioned the cambelt was at it's adjustable limit even though it'd only covered about 5-6K in that time and the balance belt showed signs of failing teeth, so I've gone for Dayco balance belt and a Gates cambelt (the cool blue 'racing' version) to see if it will perhaps not stretch as much as the currently fitted 'Conti' belt has.
Indi9xx
New member
Interesting... A belt should not stretch that much, if at all... It stretching my any real amount would mean the webbing inside it has failed across an entire cross section, which isn't good and very lucky you noticed it.
Paul's comment about outdated factory procedures is a really interesting one.
For all the Porsche models which were pre-online-Porsche-technical, registered manual administrators would be sent updates to the manuals on a regular basis. The pdf manuals that I have seen are all pretty much vanilla non updated 82 manuals, with the updated pages for the 87 revision, updated again with additional pages in 92 to cover the different S2 wiring etc, but as a whole only have the major updates, not the minor updates.
A good example that I have used before is the balance belt tensioning instructions, which in the 82 manual had an error of the tensioner being turned clockwise to tighten the belt, which of course should be anti clockwise and was released as a page sent out to manual administrators (service managers) in 83 as well as many other updates, which were pumped out on a regular basis until about 98 for the 944 manuals alone.
The last version of the manuals had instructions for a used belt under a set mileage and a new belt, with the only reference to a water pump being to check for any not rotary motion in the pump and likewise for the tensioners and rollers, with as well as bearing noise, would be mandatory to replace those components.
However in even the latest paper manuals updated with all the pages, I do not believe (I could be wrong) have no common sense with the water pumps being changed other than when play can be felt in the pulley or it is noisy... Which typically could see 40,000 miles and about 4 years that a problem could go un-detected and potentially fail if a problem only become noticeable after the job... which due to the sudden change in lateral force on the pulleys is highly likely.
My attitude of changing the water pump, front engine oil seals, tensioners and rollers on every other belt change, regardless of mileage, is just based on experience and feeling sorry for customers who experience a problem with the water pump, tensioners, rollers or oil seals half way between belt 2 and belt 3 changes... Especially those where the results become terminal for the engine.
We always check a belt about 1000 to 1500 miles after fitting one, which is based on the Porsche specification of checking it, but have found that they are still within the correct tension limits after that duration and even 4 years or 40,000 miles later... So even though we were trained that we were looking for stretch or problems, to be honest I think it has more to do with being an idiot check to check previous work before an issue becomes to grand, and to check for side effects such as a water pump not enjoying the new tension!
The balance belt tension is an especially interesting one also, with the original belt manufacturers and the Porsche engineers originally deciding on what tension level to use based on sound output, not an engineering calculation (although there would have been that in the back ground) but they agreed that a noisy balance belt was a sign of additional pressure on the belt which with the pulleys rotating at up to 14,000 rpm, was and is a real problem. I was even told off the record during training on the turbo cup cars that be best tension would be a tension just a degree less than causes the noise output of the belts to step up in volume, set with the engine running, which is the method I use on my own cars and to be honest, the method I would like to use on customers cars, but liability means I follow the instructions and specialist tools to the letter, which I do not always agree with.
Paul's comment about outdated factory procedures is a really interesting one.
For all the Porsche models which were pre-online-Porsche-technical, registered manual administrators would be sent updates to the manuals on a regular basis. The pdf manuals that I have seen are all pretty much vanilla non updated 82 manuals, with the updated pages for the 87 revision, updated again with additional pages in 92 to cover the different S2 wiring etc, but as a whole only have the major updates, not the minor updates.
A good example that I have used before is the balance belt tensioning instructions, which in the 82 manual had an error of the tensioner being turned clockwise to tighten the belt, which of course should be anti clockwise and was released as a page sent out to manual administrators (service managers) in 83 as well as many other updates, which were pumped out on a regular basis until about 98 for the 944 manuals alone.
The last version of the manuals had instructions for a used belt under a set mileage and a new belt, with the only reference to a water pump being to check for any not rotary motion in the pump and likewise for the tensioners and rollers, with as well as bearing noise, would be mandatory to replace those components.
However in even the latest paper manuals updated with all the pages, I do not believe (I could be wrong) have no common sense with the water pumps being changed other than when play can be felt in the pulley or it is noisy... Which typically could see 40,000 miles and about 4 years that a problem could go un-detected and potentially fail if a problem only become noticeable after the job... which due to the sudden change in lateral force on the pulleys is highly likely.
My attitude of changing the water pump, front engine oil seals, tensioners and rollers on every other belt change, regardless of mileage, is just based on experience and feeling sorry for customers who experience a problem with the water pump, tensioners, rollers or oil seals half way between belt 2 and belt 3 changes... Especially those where the results become terminal for the engine.
We always check a belt about 1000 to 1500 miles after fitting one, which is based on the Porsche specification of checking it, but have found that they are still within the correct tension limits after that duration and even 4 years or 40,000 miles later... So even though we were trained that we were looking for stretch or problems, to be honest I think it has more to do with being an idiot check to check previous work before an issue becomes to grand, and to check for side effects such as a water pump not enjoying the new tension!
The balance belt tension is an especially interesting one also, with the original belt manufacturers and the Porsche engineers originally deciding on what tension level to use based on sound output, not an engineering calculation (although there would have been that in the back ground) but they agreed that a noisy balance belt was a sign of additional pressure on the belt which with the pulleys rotating at up to 14,000 rpm, was and is a real problem. I was even told off the record during training on the turbo cup cars that be best tension would be a tension just a degree less than causes the noise output of the belts to step up in volume, set with the engine running, which is the method I use on my own cars and to be honest, the method I would like to use on customers cars, but liability means I follow the instructions and specialist tools to the letter, which I do not always agree with.
Indi9xx
New member
blade7 said:
I think it is potentially a fix to a problem that did not exist in a desperate rush to be able to list a number of changes to a car and be able to say "NO this is not an S2 engine"... Variocam - cool Mass airflow sensor - cool hydraulic belt tensioner, which isn't really hydraulic as such, just a damper's setup - neither cool or not cool.
Fortunately, the re-design did not end up being unreliable, otherwise that could have bitten Porsche on the bum, but seriously, there is nothing wrong with the original manual tensioner, so even the auto tensioner was really just a bit of an ill conceived fail safe for technicians in dealerships, and the 968 tensioner is just a solution to a problem that does not exist.
I inherently distrust a 30 year old spring, and did so even when they were a year old, so whatever happens I do not trust them and will check belt tensions properly as well as using the official methods and tensioners, I think though the the Porsche engineers trusted a spring more than they trusted a typical Porsche dealer technician not bothering to do things right and relying on their thumbs to set the tension, which is why I think they designed the auto tensioner (which you lock off) or the hydraulic tensioner on the 968.
I am a great believer that the less components you have in any system, the more reliable it will become, as a rule of thumb, which in theory means the original pre 87 manual tensioners are the more reliable system.
NASA paid a vast amount of cash to consultants and mathematicians in the 1960's to work out the same thing.. The unreliability of a system is directly proportional to the complexity of the system.
There are exceptions.. Points and condenser (few parts) versus electronic ignition (many components), but I struggle to find many other examples where more components results in a more reliable system.
Indi9xx
New member
Flat plastic disk with a notch in it which goes behind the distributor cap, around the shaft of the camshaft nose section that the rotor arm bolts too.
Very flimsy plastic bit, the often people throw away thinking it doesn't do anything.
944.602.803.00 from Porsche main dealers, about £10 plus VAT retail (Used to be about £2.50!) They list it as a "Dust Cap" but it's main job is to separate the electrically charged ionised air from inside the distributor cap, from the free flowing air within the belt cover. It is not air tight, but it limits the amount of airflow between the two.
Also known as an Ozone cap, searches for the effects of ozone on rubber via google should bring up pictures of the familiar cracking you see on old tyre sidewalls. Ozone is a byproduct of electrically charging air molecules.
It is not only rubber, but also other materials, such as aluminium or as a rule, anything which suffers from oxidisation or degradation in an oxygen environment tend to suffer entropy being accelerated.
Interesting is the effects of ozone on combustion, which has been found to reduce the delay between ignition and combustion. So in theory, a vacuum hose routed to a hole in the distributor cap, routed to the intake manifold, could in theory reduce oxidisation of the rotor arm tip and contacts within the distributor, as well as potentially improving performance or efficiency... However, scientific tests have found the performance increases are not measurable, even though the combustion delay reduction has been observed.
Chemistry and Physics at play.. If more performance tuners studied and showed an interest Chemistry, Physics and certainly thermodynamics, more power would result..
Very flimsy plastic bit, the often people throw away thinking it doesn't do anything.
944.602.803.00 from Porsche main dealers, about £10 plus VAT retail (Used to be about £2.50!) They list it as a "Dust Cap" but it's main job is to separate the electrically charged ionised air from inside the distributor cap, from the free flowing air within the belt cover. It is not air tight, but it limits the amount of airflow between the two.
Also known as an Ozone cap, searches for the effects of ozone on rubber via google should bring up pictures of the familiar cracking you see on old tyre sidewalls. Ozone is a byproduct of electrically charging air molecules.
It is not only rubber, but also other materials, such as aluminium or as a rule, anything which suffers from oxidisation or degradation in an oxygen environment tend to suffer entropy being accelerated.
Interesting is the effects of ozone on combustion, which has been found to reduce the delay between ignition and combustion. So in theory, a vacuum hose routed to a hole in the distributor cap, routed to the intake manifold, could in theory reduce oxidisation of the rotor arm tip and contacts within the distributor, as well as potentially improving performance or efficiency... However, scientific tests have found the performance increases are not measurable, even though the combustion delay reduction has been observed.
Chemistry and Physics at play.. If more performance tuners studied and showed an interest Chemistry, Physics and certainly thermodynamics, more power would result..
vitesse
Active member
Well neither of our 924S's have them-but our original 924 Lux had one to cover the Hall effect sensor & shield it from ill effects.
As all the distributor does on a 924S/944/968 is distribute the spark to each plug in firing order,I would image the benefit of such a shield is not measureable.
As all the distributor does on a 924S/944/968 is distribute the spark to each plug in firing order,I would image the benefit of such a shield is not measureable.
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