[alfahaze]

Hi guys,
I just bought me a 'car of the year' 1998 Alfa 156 2.0 TS. We already have a 2001 156 1.8TS with 160k miles on it.
The 1998 has 51k miles, and had the timing belt done in 2004 at 31k miles. So AlfaWorkshop in Royston recommends the belt(s) be done evey 36k or 3 years. Why every 3 years? Does this mean the timing belts have a shelf life? If so are the boxes date-stamped, and how do I know I am getting one in date? What should be my priorities on this car?
Kind regards, Hazel

 

[brinker]

So you're saying the belt hasn't been changed for 15 years? Get it done. Now.

The reason for the 3 year life, is that the belt degrades. You risk it breaking, and damaging valve and cylinder head. The biggest issue is actually the balance belt, which will take the timing belt with it, when it gives in.
The belt exchange is the same for the 1.8TS - 3 years, 36k miles. Whichever comes first. Don't skimp on belt changes, it's not worth the risk.

 

[rxe]

Twinsparks have a weak belt - it literally degrades under tension and can just snap. This is different to the V6, which usually fails as a result of idler or tensioner wear that causes the belt to rub against something.

I wouldn’t even start the engine....

 

[ronan]

Absolutely....get it done NOW !!!

It is 12 years overdue.

Just out of interest...when did your 1.8 have its last belt change ??

 

[alfahaze]

Absolutely....get it done NOW !!!

It is 12 years overdue.

Just out of interest...when did your 1.8 have its last belt change ??

The 1.8 was done two weeks ago, and then 36k miles before that. So if the Cambelt service includes the balance belt, that explains why it is £65 more expensive to do the 2.0TS than the 1.8TS. Maybe I'll book it in...

 

[johnnyroper]

You are on borrowed time with that belt, rubber degrades over time so even if it had only done 10 miles in 15 years it would still need a new belt.
Just look at tyres they have a date stamp on them and should be changed in x amount of years due to degradation despite amount of tread left. (Forget how many years they advise they last)

 

[Fruity]

That's an age record for the TS timing belt!

Yes, I don't like being overly dramatic but Russian Roulette with a loaded revolver may have less risk.

The belts weaken due to being flexed one way and then immediately the other way due to location and design of the tensioner in relation to the coolant pump.

The rubber degrades as mentioned. This can allow the atmosphere to degrade the kevlar fibres or sometimes the teeth just fall off the belt. Old pulleys can be risky mostly due to plastic rollers.

That's a good innings but I think it's overtime for a thorough belt & pulley change as well as balance belt. I'm not religious about the 36k/3 year thing but one factor being slightly extended is one thing...

 

[johnlear]

Twinsparks have a weak belt - it literally degrades under tension and can just snap. This is different to the V6, which usually fails as a result of idler or tensioner wear that causes the belt to rub against something.

I wouldn’t even start the engine....

I wouldn't want to start that particular engine either, for fear of belt breaking.

I'm pretty sure that the TS timing belt isn't inherently weaker than other timing belts (of the same width), which isn't to say that TS belts last as long most other timing belts. There is a well known history that they tend not to, probably to do with the conditions in which the belt operates. Assuming the TS belt isn't unusually narrow (?), this might be related to temperature (for whatever reason, the temperature around the TS belt in which the belt 'bathes' being a bit higher than typical with other engines?), or (probably more likely) the tension the belt is under, and / or the diameter of the sprockets around which the belt wraps (might be a bit smaller than most other engines?).

I'm no expert on this, and haven't changed huge numbers of belts on lots of different engines or made a study of it, but I do know that as an e.g. at least some Honda belts do not run anywhere near as tightly as the TS belt does. My belt experience (other than TS) is with FIAT Twin Cam (124 and 125), and with Honda F and D series engines (Accord and Civic etc). The old FIAT Twin Cam engines had a recommended belt change interval of 40,000km or four years, but the OE belts were of much lesser quality / strength than modern belts (no kevlar back then). Honda belts are recommended changed at well over 100,000km or 6 years (somewhat less if the engine is operated in a very hot climate), and are not known to be problematic if changed according to recommended interval.

With the Honda engines, the spring which tensions the belt is very much weaker than the TS belt tensioning spring. Also, with these Honda engines the belt isn't 'actively' tensioned, the weak tensioning spring only 'pre-loading' the belt during installation, the tension then being 'locked in' by tightening a nut. The end result is that these Honda belts are almost loose, with only a very light tension acting on them (so light that I would manually 'add' just a tad more tension with my finger as I tightened the lock nut...).

The FIAT Twin Cam engines also don't run 'active' tensioning (i.e. instead are 'pre-loaded' and the tension 'locked in' by tightening a nut), though the 'pre-loaded' tension is much higher than the Honda engines (possibly approximately similar to the TS belt tension, but it's been a while since I played with a FIAT Twin Cam engine). With either the Honda or Fiat engines, the belt tension does seem to lessen over time, as even a minute amount of belt stretch will see a significant loss of tension (with both FIAT and Honda engines I've seen old belts that were running effectively zero tension at time of replacement, yet hadn't 'jumped a tooth'...).

By comparison, the TS tensioning spring is much stronger than the Honda tensioning spring and places the belt under a LOT more tension. The tension isn't 'locked', the spring is 'active' and always fully acting on the belt, which isn't the case with the FIAT or Honda belts. So, for all of its' life the TS belt is running at 'full tension', but for the Honda and FIAT engines the belt only runs at full tension for some of its' life, lessening over time (and with the Honda engines, 'full tension' is not very high to start with, and the belts don't usually 'jump' or are otherwise problematic).

Also, the tight belt will be placing more load on the bearings in the water pump and idler pulleys, so these may also have a shortened life expectancy due to the substantial belt tension.

So, Alfa may have their reasons to run a high and 'active' belt tension, but I suspect it may be related to the relatively short belt life. This doesn't seem to be something that the Alfa engineers predicted, since the original recommendation for belt change interval was much longer than the later 'revised' recommendation...

Regards,
John.

 

[alfahaze]

I'm not a fan of timing belts per se. However I did read the patent for the Busso V6 de-tensioner. It is very clever and uses the oil pressure of the engine to de-tension the belt. However when it leaked belt slippage was more likely. My first belt broke during decelleration (Alfa V6) My second belt was fine, even though the valves got stuck and the pistons chewed up every valve in the head, the belt was good. Second belt to slip was on an Astra, again during mild decelleration. I drove the 156 today very carefully, with no sudden decelleration, I think I will book it in for belt replacement...

 

[Spider95]

I'm not a fan of timing belts per se. However I did read the patent for the Busso V6 de-tensioner. It is very clever and uses the oil pressure of the engine to de-tension the belt. However when it leaked belt slippage was more likely. My first belt broke during decelleration (Alfa V6) My second belt was fine, even though the valves got stuck and the pistons chewed up every valve in the head, the belt was good. Second belt to slip was on an Astra, again during mild decelleration. I drove the 156 today very carefully, with no sudden decelleration, I think I will book it in for belt replacement...

Well I think you're very brave driving it at all. 15 years since last belt change is probably a record. Not only there is danger from the belts themselves you probably have the old white plastic composite tensioner which was known to fall to pieces - it was replaced with a metal version.

Quite honestly you are now well beyond borrowed time and are now playing Russian Roulette - except all the chambers are loaded with bullets. :titanic:

 

[ronan]

I'm not a fan of timing belts per se. However I did read the patent for the Busso V6 de-tensioner. It is very clever and uses the oil pressure of the engine to de-tension the belt. However when it leaked belt slippage was more likely. My first belt broke during decelleration (Alfa V6) My second belt was fine, even though the valves got stuck and the pistons chewed up every valve in the head, the belt was good. Second belt to slip was on an Astra, again during mild decelleration. I drove the 156 today very carefully, with no sudden decelleration, I think I will book it in for belt replacement...

Well I think you're very brave driving it at all. 15 years since last belt change is probably a record. Not only there is danger from the belts themselves you probably have the old white plastic composite tensioner which was known to fall to pieces - it was replaced with a metal version.

Quite honestly you are now well beyond borrowed time and are now playing Russian Roulette - except all the chambers are loaded with bullets.

I agree....next trip I would take is to the nearest mechanic.

 

[gazza82]

It's been every 3 years since 2001!!! And I made one last 7 years .. the engine wasn't pretty after it failed. And what failed was NOT the belt .. that was still pretty good .. the tensioner seized and ripped teeth off the belt. When that section got to the crank gear .. the belt stopped .. the pistons didn't!

And only 51K? Mine got to 210K! Keep an eye on the inner sills and floor ... the sealant traps moisture!

 

[johnlear]

I'm not a fan of timing belts per se.

Belts do have advantages over chains. Probably cost (to manufacturer...), quietness, and (as I understand it) stability of valve timing at higher rpm. This is due to the belt having significantly less mass than a chain and therefore lower inertia. Due to its' mass, at higher rpm a chain tends to not maintain a perfectly straight line (or the as designed shallow arc created by the shape of the chain guide) on the direct run between the cam sprocket and the crank sprocket, but assumes or tries to assume a shallow sinusoidal "S' shaped curve (more so as rpm increase).

Any mass in motion 'wants' to travel in a straight line, unless forced not to. As the (relatively heavy) chain wraps around the camshaft sprocket it is forced to change direction (horizontal to vertical), but tends to be 'thrown outward' by kinetic energy as it 'leaves' the camshaft sprocket. This causes the chain to not exactly follow a straight line between sprockets, but a slightly curved line. The resistance to rotation of the camshaft and the driven force of the crank sprocket isn't enough to overcome this at higher rpm, but does affect the shape of the curve. Instead of the chains' curve being a simple arc between sprockets, it becomes the shallow "S' shape mentioned above, affected by harmonics and other arcane effects I don't really understand...

With a single cam engine the problem only exists between the camshaft and crankshaft. In a twin cam engine the problem exists most strongly on the long chain run between the 'second' camshaft and the crankshaft, but also exists to a lesser degree on the short chain run between the two camshafts. Chain guides help a lot, but don't completely eliminate this problem. Because of the chain guide inhibiting the "S' shape from forming, the problem is likely to manifest as chain 'snatch'.

Because the shortest distance between two points is a straight line, any deviation of the chain path from being in a perfectly straight line (or the controlled arc imparted by the guide) causes the camshaft to over rotate, thus causing the valve timing to become somewhat advanced. Dynanmic harmonics in the chain causes the 'depth' of the 'S' shaped curve to vary at different rpm (and whether the engine speed is increasing or decreasing etc.), and with each variation in the depth of the S curve (i.e. the effective length of the chain bewteen sprockets) the over rotation of the camshaft increases or decreases, and the valve timing becomes in some degree 'scattered'. If the ECU relies upon a camshaft position sensor then the ignition timing (and injection timing?) will also become 'scattered' at high rpm.

For an engine that doesn't rev particularly high this is all a minor issue at most, but belt camshaft drives (with the belt being lighter and therefrore having lower inertia) are less prone to it and can rev higher without it becoming an issue (even without a 'guide' for the belt). It is likely the main reason why high revving purpose built racing engines (as opposed to road car engines modified for racing purposes) are usually designed with a train of gears to drive the camshafts rather than a chain or belt drive (complicated, expensive, and noisy, but provides stable camshaft rotation speed relative to crankshaft speed).

After writing the above, I did some quick 'research' to double check that I wasn't talking through my arse. I stole the following paragraph from this paper:

https://www.cg.tuwien.ac.at/research/publications/2007/Konyha_2007_SCV/Konyha_2007_SCV-Download paper.pdf

"The chain’s motion deviates from its ideal kinematic path especially at high engine speeds. Dynamic and inertial phenomena cause vibrations that increase noise levels and mechanic wear. The vibration causes the accuracy of the motion coupling to deteriorate. The camshaft’s rotational velocity does not remain constant and undesired high frequency components are added. This induces rougher and less controlled valve operation which can reduce fuel economy and power output."

I drove the 156 today very carefully, with no sudden decelleration, I think I will book it in for belt replacement...

With a fifteen year old belt, either brave, or foolish I don't care to judge you, but definitely lucky...

Regards,
John.

 

[Fruity]

All timing belts tend to have dynamic tensioners in recent years. There is less tension variation than with static types. Belts tend to use similar tensions with regard to design (trapezoidal or spherical tooth design). Too loose, they rattle and teeth fall off, too tight they whine and weaken the valley area).

Modern engine belt routing has become more compact. Smaller pulleys and faster bending of the belt increases loading on the belt. Twin cam engines produce greater camshaft speed fluctuations and greater reverse bending which accelerates belt fatigue.

Alfas and Fiats use the Pratola Serra family of engines. The Alfas use hotter profiled camshafts. That's why Fiat never had as severe timing belt issues.

Usually it is only diesel engines which have HTS (High Temperature Stable) belts. More heat escapes down the exhaust pipe on petrol engine but more heat radiates from the combustion chambers on diesels. That's why diesels have HTS belts.

 

[johnlear]

All timing belts tend to have dynamic tensioners in recent years. There is less tension variation than with static types. Belts tend to use similar tensions with regard to design (trapezoidal or spherical tooth design). Too loose, they rattle and teeth fall off, too tight they whine and weaken the valley area).

The Honda belts do have the rounded tooth profile (if memory serves), and the Alfa TS engines do have the more square section - trapezoidal - teeth (can't recall with certainty what the Fiat Twin Cam belts had, but I think was squarish section teeth). I can't imagine how the tooth shape would affect what tension a given belt may require.

I do note that the Honda engines of which I'm speaking are single cam engines, perhaps twin cam Honda engines of similar era (e.g. the H22A series) have a stiffer belt tensioning spring, but looking at online photos suggests they are similar to the (weak) tensioning spring on the single cam engines...

The Honda engines I've mentioned are quite 'modern' in the evolution of fundamental engine architecture, and still used 'weak' 'static' belt tensioning quite successfully (I'm sure Honda could have used 'dynamic' tensioning had they so wished or deemed needed, and / or stronger tensioning). By 'successfully' I mean very reliably with extended change intervals (unlike the TS Alfa engines with substantial 'dynamic' belt tensioning). Whether or not later Honda engines retained 'static' tensioning I don't know.

I can say from experience that the Honda belts I've seen are barely tensioned by the tensioning spring. The spring is so weak it would hardly take the slack out of a new belt, hence my practice of giving the spring a 'helping finger' when installing belts, just enough to ensure that all slack was eliminated (but still not 'tight' by any stretch of the imagination). I therefore do still wonder why Alfa found it necessary to use such substantial belt tension, since it obviously isn't needed with other engines of not disimilar basic design, and whether or not it may actually be problematic...

Modern engine belt routing has become more compact. Smaller pulleys and faster bending of the belt increases loading on the belt.

As I (think I...) understand this, smaller pulleys or sprockets don't impart greater tension into the belt or chain (i.e. the tension that results primarily from driving the camshafts against the stiffness of the valve springs, not the as fitted belt tension, which is also unaffected). The crank / camshaft pulley ratio is always a leverage ratio of one to two regardless of the pulley sizes (given that the camshafts must rotate half a rotation per one crank rotation). This means that if the drive pulley rotates 180° then the driven pulley must rotate 90°, and the camshaft pulley 'lever arm' must be twice the length of the crankshaft pulley 'lever arm', so no matter the pulley diameters the end of one lever arm must move half the distance that the other lever arm moves (or vice versa), or else the leverage ratio becomes other than one to two.

With a smaller radius crank pulley, the crankshaft can pull against the belt more strongly (i.e. the belt tension has less leverage acting against the torque at the crankshaft, and so the belt moves less per degree of crank rotation). But the camshaft pulley will also be smaller (to maintain the one to two leverage ratio), so there is less leverage acting on the camshaft via its' sprocket, so the camshaft is less able to resist the force imparted by the smaller crank pulley. So, as long as the pulley ratio does not change, then the force (tension) imparted into the belt will not change, even if the forces 'seen' at each pulley does change, it all comes out in the wash...

I do agree that smaller pulleys (in particular the inherently smaller anyway crank pulley) may well shorten belt life due to repeated 'over' flexing of the belt around the smaller radii sprockets, creating somewhat greater physical stress (kevlar fatigue?) as well as some slight increase in running temperature (the kevlar belts probably aren't affected much if at all, but bad for the rubber component of the belt, given time).

Twin cam engines produce greater camshaft speed fluctuations and greater reverse bending which accelerates belt fatigue.

"Greater camshaft speed fluctuations"? Not sure about that. Twin camshaft engines do impart stronger fluctuation in the load the belt experiences, because each camshaft only has half the total engine valve loadings associated with that camshaft (i.e. only the inlet valves or only the exhaust valves), meaning that each (belt loading) valve opening event is more separated from the other loading events, i.e. less overlap between them. This creates greater spikes in the loadings experienced by the belt, even if the highest loading level that the belt experiences may not increase.

As I understand it, this increase in tension variation is only seen in the belt run between the two camshafts, the long belt run between the 'second' camshaft (whether it be inlet or exhaust camshaft) and the crankshaft experiences all the valve opening events with less fluctuation between them (unless perhaps the section of belt between the camshafts is experiencing fluctuating loads to the point of becoming loose tight loose tight, which I suspect unlikely unless the belt has some actual slack in it...).

Single cam engines have all the valve loadings associated with only the one shaft, so there is more loading overlap and so the belt tension fluctuates less. Either way, strong fluctuations in belt tension are probably bad, so minimising them should be a good thing, but it will be what it will be for a given architecture.

Alfas and Fiats use the Pratola Serra family of engines. The Alfas use hotter profiled camshafts. That's why Fiat never had as severe timing belt issues.

The FIAT 'Twin Cam' engines are quite different and much earlier than the Pratola Serra engines (replaced by the Pratola Serra series). They were developed from an (earlier still) OHV pushrod block by Aurelio Lampredi (ex Ferarri engine designer), and the first (or at least among the very first) production engines to eschew chain for belt drive.

It may be that the more 'ambitious' valve timing associated with variable valve timing at higher rpm may be a factor in reduced belt life, but the lift and duration of each individual opening / closing event isn't typically affected by this, so I tend to doubt it...

Usually it is only diesel engines which have HTS (High Temperature Stable) belts. More heat escapes down the exhaust pipe on petrol engine but more heat radiates from the combustion chambers on diesels. That's why diesels have HTS belts.

I'm sure belts don't like higher temperatures, I wouldn't if I were a belt...

Regards,
John.

 

[Fruity]

Yes, ok not all my information was completely accurate but you got my drift.
More valves, separate camshafts for inlet and exhaust valve duties, more compact architecture and more alignment-critical components such as coolant pump all take their toll. Yes, I knew you meant the old Fiat twin cams but the comparison of Fiat and Alfa Partola Serra units was to illustrate how the belts are loaded closer to a critical point simply from different camshaft profiles. It all takes a toll.

Yes, it is a shame cam belt life us so poor when VAG were consistently 72k around that era. Some newer diesel engines are now supposedly twice that but cam belt failure incidence of any engine with a belt above 100k (miles) is higher than people realise. It's not surprising really but at least newer turbocharged petrol engines should have less stressed timing belts.

I think that real world tests and possibly design was omitted from our engines in order to keep costs down. I think that is illustrated by the amount of deviation from original service schedules or using higher spec products than stipulated in order to keep our engines reliably performing well.
In other words, we have had to do a bit of R&D.

 

[alfahaze]

I played russian roulette three more times today. I had to replace the rear pads, as they had hit the rivets. I've booked in for Tuesday, which will be the final russian roulette.

I would be curious to know if the failures that prompted alfa to reduce the cam belt interval were on cars by the coast, or those with the undertray removed, both of which maybe are factors in premature belt system failure, and probably were not scenarios tested by Alfa.

 

[johnlear]

Fruity,
I do agree with most of what you say.

I said;
"I therefore do still wonder why Alfa found it necessary to use such substantial belt tension, since it obviously isn't needed with other engines of not disimilar basic design, and whether or not it may actually be problematic..."

I later realised that (of course...) if a belt is 'dynamically' tensioned (i.e. not 'locked in' by preventing the tensioning pulley from moving in service), then by that very fact it will be necessary to use a substantially strong tensioning spring, which will inevitably result in a tight belt. If not very tight then the belt will be in great danger of jumping the pulleys because a weak 'dynamic' spring will easily 'over stretch' and the belt will become slack and jump the pulleys. So it seems (to me) that fitting the belt very tightly isn't necessarily a design goal of itself, but may instead be largely a by-product of the engineers' initial decision to use a 'dynamic' tensioner rather than a 'static' tensioner.

Having said that, the old Fiat Twin Cam engines did have a tight belt as well as 'static' tensioning, but it can't be the other way around, i.e. not a lightly tensioned belt with 'dynamic' tensioning. The early Twin Cam engines had no tensioning spring at all, the static belt tension being set using a simple spring loaded weighing scale temporarily attached to the tensioner (i.e. a spring inside a tube with a pointer and weight readout on the outside, used to weigh 'things'), by applying 27kg of linear force to the tensioner while then tightening the 'lock in' nut. That is a lot of belt tension considering that the Twin Cam engines' belt would quite happily run with far less tension and not jump teeth (as evidenced by stretched Twin Cam belts losing most of that initial tension and still running reliably), and by other engines having no problems using a lightly tensioned belt with a 'static' tensioner.

So now I do question the wisdom of the design decision to ever specify a 'dynamic' belt tensioner in preference to a 'static' tensioner, considering the increased strain that 'dynamic' tensioning appears (on the face of it) to impose on the resultingly very tight belt (and on other components driven by the belt...). Why? What real advantage does 'dynamic' tensioning and a tight belt offer over 'static' tensioning and a lightly tensioned belt? Seems to me to be fundamentally more problematic than helpful, unless I'm missing something...

End users should not be having to do the basic "R&D" which the factory ought to have sorted before going to market with a given design. It is what it is, but seems a bit sloppy and disappointing. Having said that, I'm not brave enough to attempt engineering an alternative light tensioning 'static' tensioner for my own TS engine, even if I think it might be a better way to go than the factory did...

Regards,
John.

 

[Spider95]

I played russian roulette three more times today. I had to replace the rear pads, as they had hit the rivets. I've booked in for Tuesday, which will be the final russian roulette.

I would be curious to know if the failures that prompted alfa to reduce the cam belt interval were on cars by the coast, or those with the undertray removed, both of which maybe are factors in premature belt system failure, and probably were not scenarios tested by Alfa.

The original scheduled belt change was probably too optimistic. The routing of the cambelt itself is not really the best on the TS engine for longevity, and there are multiple factors that may lead to cambelt failure, including of course the cambelt assembly itself.

For instance, Alfa Romeo have changed the tensioner three times: 1) The original black composite tensioner, 2) the white composite tensioner which was admittedly very quiet but had a tendency to break up, 3) the current metal tensioner which is proving more resilient, but takes it out more on the belt (for obvious reasons). You can build in lots of other factors - frequent stop/starts, warmer climates (not good for belts due to the process of vulcanisation in warmer temperatures), the list is endless. Alfa settled on changing the cambelt change interval to 3 years/36,000 miles in 2006, simply to try and cover all scenarios.

When you get your cambelt kit changed on Tuesday make sure the full kit is changed - cambelt, cambelt tensioner, cambelt idle bearing, balance belt, balance belt tensioner. Also change the water pump and coolant at the same time.

 

[alfahaze]

The original scheduled belt change was probably too optimistic. The routing of the cambelt itself is not really the best on the TS engine for longevity, and there are multiple factors that may lead to cambelt failure, including of course the cambelt assembly itself.

For instance, Alfa Romeo have changed the tensioner three times: 1) The original black composite tensioner, 2) the white composite tensioner which was admittedly very quiet but had a tendency to break up, 3) the current metal tensioner which is proving more resilient, but takes it out more on the belt (for obvious reasons). You can build in lots of other factors - frequent stop/starts, warmer climates (not good for belts due to the process of vulcanisation in warmer temperatures), the list is endless. Alfa settled on changing the cambelt change interval to 3 years/36,000 miles in 2006, simply to try and cover all scenarios.

When you get your cambelt kit changed on Tuesday make sure the full kit is changed - cambelt, cambelt tensioner, cambelt idle bearing, balance belt, balance belt tensioner. Also change the water pump and coolant at the same time.

I did request the water pump changed on our 1.8TS a couple weeks back, but they (Alfaworkshop) said it was fine, and they usually just keep going. That water pump has 165k on it!!! It has seen out an expansion tank, a radiator, two thermostats and a couple of hoses. Of course the 2.0 is different animal what with the balance belt and all. It really is a smooth engine.