KV6 teenage timing belt exposed at last!

[Simondi]

Originally Posted by SD1too

My apologies Simon. I made an incorrect assumption. It's a shame that it was never determined why your belt broke within the 6 year and 90,000 mile period. You were genuinely unlucky there.

Simon

I refer you to my earlier post lol

[Simondi]

A wee summary if I may.

Manufacturer specs for KV6 belts is 90000 miles or 6 years.
Experience shows that on the whole belts can and do last longer than the manufacturer specs.
What does this mean?

1. Regular maintenance and inspection of the engine, belts, tensioners etc is vital.
2. Any doubts or concerns should be acted upon
3. If you are unsure on the cars history, err on the side of caution
4. If you know your car, know it's well maintained and are approaching or have passed the 90k/6 Year mark then don't panic. The car probably won't t self destruct.
5. Unless you have the skills, leave it to a professional

[rovertone]

I recently replaced a belt on a VW Polo, a job I had been putting off for a while, but I had bought the belt in readiness. When I came to do the job I was surprised to find that the belt had a 'use by' date on the box which was just about to expire. The belt was as new but after a bit of soul searching I scrapped it and bought a new one.
This was a genuine VW belt, do all mfrs show a shelf life? This would suggest that it's age and usage related criteria for replacement.
I've got a 54 reg Rover 25 with just 26K on the clock and I have just changed the belt on that for the first time, I must admit I wasn't comfortable driving it about with such an old belt, albeit the old belt looked as good as new.

[slovcan]

Man, this thread is like a huge car crash on the highway. You really don't want to look, but can't help taking a glance. 7 pages! I got to page 5. I'm out. Can't take any more of this nonsense.

[roverbarmy]

Originally Posted by slovcan

. You really don't want to look, but can't help taking a glance.

Reminds me of a "lady" I used to know who always wore her skirts too short, her blouses too low and was really much bigger than her clothes!!! Cheer up folks. Live and let live. Pay yer money and take yer choices - or not!

[Teflon]

Been following this with interest. Personally, I have no technical quals, and leave all the techy stuff to folk that are more qualified than me and have earned my trust.

That said, I do have a little theory (prepare yourselves!) based on nothing more than my rambling thoughts. Here goes:

What Simon says regarding belts only wearing whilst in use does seem logical to me, however it got me wondering what causes the most wear. It seems logical to me that the most stressful part of a belts life is probably when the engine is started and the belt goes from stationary with no (or very little) strain to tickover (or more if the car is "revved") in a fraction of a second.

If that assumption is correct, Putting myself in the manufacturers position, I wondered how I might go about setting a replacement recomendation. 90,000 miles may seem reasonable for "normal" usage, however, it doesn't take account of how many times the engine is started. A vehicle used purely for very short trips will incur many more engine starts than average, so may suffer premature wear in terms of mileage (but only if my assumption is correct ). Obviously, I couldn't set a recommendation of "X" amount of engine starts, so the next best thing would be to set a time limit in order to cover low mileage cars with frequent startups. Perhaps that's what's behind the 6 year recommendation and possibly why some belts appear to survive better than others?

I'd be interested to hear your thoughts on the startup theory Simon. As I said, I've no quals or relevant experience to back up my thoughts, so I could well be barking up the wrong tree completely .

In the meantime, good luck with completing your belt change. Having watched Lates do mine, I've seen the amount of work involved .

Cliff

[SD1too]

Originally Posted by Les4048

... most are sensible and stick to the recommended service intervals ... You’d have to be incredibly naive to do anything else ..

So you consider that I lack experience, wisdom or judgement then Les. I'd say that as I had the courage of my convictions to "risk" (in your view) running my car on the original belts and have had my judgement proved right, then I am anything but naive. I am, though, in the minority and Ghandi had something to say about that:

"Even when you are a minority of one, the truth is the truth".

Originally Posted by Simondi

... inspection of the ... belts, tensioners etc is vital.

I agree with your summary Simon except for the above, only because it is impractical to inspect the front timing belt and tensioner without an enormous amount of dismantling. So really, the choice is whether you do this work on a time or mileage basis.

Originally Posted by rovertone

... I was surprised to find that the belt had a 'use by' date on the box ... This would suggest that it's age and usage related criteria for replacement.

No, it's just the marketing department ensuring the commercial survival of the company Tony.

Originally Posted by Teflon

Been following this with interest ... I've no quals or relevant experience to back up my thoughts ...

Thanks Cliff and don't worry, not having formal qualifications or direct experience shouldn't stop anyone having a good and relevant idea.

It seems logical to me that the most stressful part of a belt's life is probably when the engine is started and the belt goes from stationary with no (or very little) strain to tickover (or more if the car is "revved") in a fraction of a second.

I agree and this has been raised today by another member.

A vehicle used purely for very short trips will incur many more engine starts than average, so may suffer premature wear in terms of mileage ... Perhaps that's what's behind the 6 year recommendation and possibly why some belts appear to survive better than others?

I think that's a sound theory Cliff and is exactly what Citroën did. They specified a lower mileage for "severe use". Among other things this included frequent short journeys under stop-start conditions. I renewed the cambelt accordingly. I need not have bothered. The exisiting belt was in perfect condition.
But if that's what MG Rover meant, why didn't they say it?

... good luck with completing your belt change. Having watched Lates do mine, I've seen the amount of work involved

Yes, it's quite daunting isn't it. Still, I've done comparable tasks before such as diagnosing and successfully fitting a reconditioned torque converter, gear train unit and brake bands to an AP automatic transmission. I saved about £1,200 on that repair and the gearbox worked better than it ever had after previous attention from "the trade"! Not bad for someone who Les4048 and MarinaBrian thinks is incredibly naive, eh.

Simon

[mbonwick]

Originally Posted by SD1too

That's good to hear Michael. Can you let us into the secret about belt failure then. What actually causes some belts to apparently fail and others not over the same time period?

Is that going to be studied with a large range of sophisticated kit to discover the reason?

It wasn't sent to mbonwick's company by any chance was it?

Simon

In order:

Once rubber is vulcanised, it never stops curing - i.e. it progressively gets harder and more brittle with time no matter what. There are hundreds of variables that influence this from initial chemistry, curing temperature & time; to storage and then service conditions (temperature & cycling, contaminants, stresses (usage), damage) etc etc. So every belt is pretty much unique in terms of properties by the time it makes it onto the car, and most of the degradation is at a molecular level so cannot be observed by the naked eye (although some of the more extreme effects, e.g. cracking/crazing may be - but they don't always occur).


My aux belt will not be examined as its long gone in the bin! However, what my qualified eye saw with a magnifying glass was suggestive that failure had initiated in the cord and not the rubber.

Finally, work won't be examining any belts, even though we have the kit to do so, as we're exclusively focused on building the UKs underwater military defence....big, black, hard to find tubes if you catch my drift

[chrisk]

I started the car tonight after doing the belts my wife's 55K miles V6 auto for my first time. I was a bit worried when it didn't start, but I'd re-fitted the fuel pipes the wrong way round.

If you've decided you want to change your belts, I thought I'd record a few of things that I hope I remember next time. After a neighbour who worked in the trade told me it was 4.5 hours book time, I felt like a snail.

The service book in the car indicated that the belts had been changed in 2015. They hadn't, the front looked ancient and the noise that alerted me to the doing it was caused by the belt slipping on the water pump. I could turn the pump by hand with the belt on it was so loose. A close call.

First, and I never learn, avoid doing it on a slope if you can. It's a nuisance.

The crank pulley has moved around on my wife's car and I wasted too much time trying to align the marks. As someone else said, use the notch on the camshaft sprocket to be sure. On the same subject, I tried to find the 69mm tool to hold the camshaft pulley while removing the bolt. One place sells it, but it's over £100 on back order and the car only cost £590. I resorted to my Lidl mains impact driver to get it off and used a £39 12v digital adjustable automatic one to re-fit it at the correct torque. If you have a manual car, no problem.

I read lots about belt tools on here before starting. I had found some in the US on the well known site for £50 ages ago. They are fiddly to use, but I was glad I had the front tools given the crank pulley issue. I was sure everything was lined-up a and refitting was straightforward. The rear tool is a complete waste of time. The spreader thread went after one try and it is easier to feed the small belts over the top pulleys using the long pins in the kit while someone holds the camshaft against your marks on the backplate. Make your own marks: someone had done this before and they were all over the place. If you have the front tools, you can use them to turn the camshafts to align the rear sprockets.

I read the sage advice about leaving the rear AC compressor bolt in place. I can see why. It took ages to get these out (patience was vital as it would have been a nightmare if they had rounded). If you loosen the AC pipes under the radiator you can hold the extension in a straighter line to loosen the three compressor bolts. I ordered new ones from Rimmers.

I think a gorilla had removed the manifold top cover previously. Most of the breather connections were chipped on the throttle body and manifolds and the two rear brackets were long gone. The black connectors on the throttle body only require a gentle push with a screwdriver to remove them.That's a problem for another day.

Ah yes. If you have an auto, follow the Haynes book advice and drain the oil. It seems to flow for days if not when you remove the dipstick. I was trying to save new oil but only ended up paying to buy stuff to clean the drive.

I have a Ducati and I was quite excited about harmonic belt tensioning on a car with an app. Another waste of time. I used the pin method (the pin is in belt tool kit, but it's just a pin).

My bro's MG ZT is next. I hope I can do that in half the time.

It sounded great tonight. Fingers crossed we have no leaks or squeaks.

[neilll]

Simon,
To give everyone a benchmark on when to change there belts, why dont you leave yours ( you dont seem to be in a hurry to change them,as you seem to be on your P.C. rather than in the garage) until they let go! We can then all drive our cars as we do until 1 mile before yours let go!!!!
Neil