Ok so my dear daughter bought her first car with a friend's help. They made a pretty good job of it .. but did not ask about the maintenance - specifically timing belt and tensioner replacement. So, you guessed it, 115K miles and no change! Well I was happy to do it and check things over generally. On the way back (130 mile journey) I discovered the front shocks were shot, so contemplated replacing the front suspension components and brake disks and pads. First off not even a large braker bar or torque wrench would shift the front wheel bolts. A trip to the local tyre fitter did the trick but they only just managed.
Well, long story short, I returned to have a wheel alignment and then set out on the return journey. An hour later on the M40, a tell-tail noise alerted me to trouble with the front end. I stopped at a services and found the n/s front weel bolts loose. One would not tighten even hand tight! Moral, do not over tighten bolts. they stretch and are afterwards prone to snap. Just to round off I got two very new looking bolts off a scrappy today (and dirty hands for £1.00!

115k miles on original timing belt? another timing belt change interval debunked

It wouldn't surprise me that a belt could last that long , no more than a failure at 30 000 miles would. It cuts both ways. The specified interval is to keep 99.999% of us out of trouble.
Just because no belt change was recorded doesn't mean it didn't happen.
Absence of evidence is not evidence of absence

and how did they come to the number that states when you should change it?
probably marketing trick!!

flisko said:

115k miles on original timing belt? another timing belt change interval debunked

Click to expand...

Im at 80K Now
No belt history - cant tell markins have worn off but i believe to be original all the way

so its 8k Over now, its also many years past its best, yet i've got no issues?

I do think with the fire engine - wait till it snaps but only if you know how to replace it

Ziggy

flisko said:

and how did they come to the number that states when you should change it?
probably marketing trick!!

Click to expand...

Give them the benefit of the doubt. Fiat want you to come back so they give you their best shot. It won't be perfect but if we wanted that we couldn't get out of bed in the morning.

Well the interval is probably on the safe side. I rather do an early swap than have it snap halfway while driving. That would ruin my day and I would also need to get it towed in.

flisko said:

and how did they come to the number that states when you should change it?
probably marketing trick!!

Click to expand...

I'd be interested to hear how you would calculate the service interval.

Here's what happens.
The lab rats measure belt life to ten places of decimals at a level of 6 sigma.
The warranty people say No , this is what worked last time and anyway our typical customer can only handle even thousands of miles.
The marketing guys say you are all wrong. Opelundaifordgeot have just offered 30 000 km service intervals

atom0007 said:

I'd be interested to hear how you would calculate the service interval.

Click to expand...

Normal practice is material samples are tested at elevated levels to give a worst case life, in service experience is added in and a "safety factor" added. That said I'd expect a factor of 2 applied to the 95% failure time, so 115k is not unexpected but you how have a high probability of failure. There is a lot of information on flexible drive belts out there.
As an aerospacee engineer we reguarly have to reguarly come up with reliabiity figures for equipment and designs and there are established processes for doing this. Similar drive belts are used in aircraft, even for the main rotor transmisson on a number of small (2-4 seat) helicopter designs.

Robert G8RPI.

In the majority of cases, it's not the belt which fails per se but the belt tensioner bearing. The tensioner lets go its perch and mangles the belt or simply unseats it from the pulleys. Another scenario is one of the auxiliary belts failing and in turn taking out the timing belt. An often overlooked replacement item is the AOC on the alternator, basically the alternator has a clutched, freewheeling pulley that smooths out the tendency of the belt to snatch. This normally has a service interval complimentary to the timing belt. On my 15 year old 2.4 l low pressure turbo 5 cylinder Volvo it is 110K or ten years. I paid about £350to have it done. But back to the Punto 8v and really it is very easy to do yourself for the price of a conti belt and a day off road.

By coincidence out other bus is an elderly V70 D5. Any timing belt disaster I've come across has been due to trouble at the aux belt. Either the alt freewheel or the tensioner idler pulley.
Our Punto threw a timing belt and it was due to the crank pulley ingesting the alternator belt after it shredded.