The other day I had my 2007 XJR car at the local dealer and they recommended changing the supercharger and serpentine belts. I looked at what little is visible of the belts and couldn't see any micro-cracks or missing chunks. The car has 61K miles and AFAIK has never had the belts replaced - I always thought 100K was the life of modern belts?

 

Let us know when it fails, then . And what costs that failure entails.

Ex; Pushed the non-metallic fibre timing gear on my Sonoma pickup a few tens of thousand of miles further than was wise (~ 145K). New all-metal set, cover and sealant were cheap enough, and not hard to install.

Flat-bedding the b*** home from where it had died, OTOH, was a serious chunk of change @ $50 callout plus ten bucks a mile.

Belts are easier, and all types - save perhaps Morse Rocker-link - are cheap enough I don't care to find out if they will even last beyond 50K miles. Or sometimes 30K, (OHC Gilmer belts).

 

Thermite,that is a ridiculous comparison you have made----timing device failures are usually much more severe than auxiliary drive belts.

If you check your owners manual and the recommended service intervals,Jaguar recommend replacement of the front accessory drive belts at 100,000miles.The supercharger drive belt they recommend changing every 40,000 miles.Obviously you should check regularly for cracks etc and change if the belt becomes defective.
(For my S-TYPE the change interval is 150,000 miles!)

As a matter of prudence I carry tools and spare auxiliary drive belts(among other things) in all my cars.

 

Surely - insofar as internal engine damage. BTDTGTTS. Sonoma's I-4 had non-interfering valves and pistons. A '68 Fiat 124 earlier in my 'learning curve' was another story entirely.

But how far do you figure you can run a Jaguar V8 with the serpentine belt gone and no coolant being pumped?

Yer probably up for a tow either way. Roadside repairs are not just inconvenient - they are a safety risk.

I suggest putting the new belt on the ENGINE well before 100K miles, then stashing the OLD belt in the boot if it doesn't look too bad. Far less likely to give you unplanned grief.

 

Thanks - probably makes sense to have both replaced at the same time, then.

 

ACK.

If hiring it done, mebbe 70% to 80% of the labour is just to just get access, perhaps clamp motating bits & unclamp - then close-up afterwards. The belts themselves less-costly than the hourly.

When DIY, it is the time and aggravation of making two goes at it instead of one. Or at a time and place not in the plan...

'Wasting' still quite-serviceable belts is usually the cheapest part of either deal.

We can only wish that an engine or transmission could be dealt with the same way... as Buick did once do. Roll-out engine at one end, roll-out transaxle at the other.

But not your 'average' Buick. A predatory feline, and devised of necessity...

...the M-18 'Hellcat' Tank Destroyer.

Speed-daemon that it was, right sorry ride-comfort and MPG vs any Jaguar ever made.

 

keeping a used, but servicable,, belt in the boot is a good idea. If you have to change a belt in inconvenient circumstances, an old one is easier to handle as it is more flexible so easier to fit. Clean it before putting it away and inspect for wear and damage.

It is many years since I last had a belt fail in service, and I certainly wouldn't change them at 60k

cam belts, in vehicles that have them, are more serious so worth changing at maker's recommendation, though on a previous car I had one changed at recommendation, and the old one looked and felt like new. Proper cars have chains, of course.

 

Nah.

'Proper' OHC engines have straight-cut spur gears.

Music that fires the blood, those.... well .. memories anyway ..

Now .. .where'd I leave my heart pills?

 

Depends.

Mileage / engine hours are but one of several factors affecting rubber and other elastomerics.

Here in suburban Metro DC ozone is not a factor, as our only 'Heavy Industry' - the US Gummint - sucks all of the oxygen out of the entire Mid-Atlantic and turns it into hot-air more corrosive to human cooperation than to mechanicals.

Hong Kong, Shanghai, Beijing, et al of today, or Bayonne, NJ, and Pittsburgh and West along the Great Lakes when 'merica still manufactured things onshore, OTOH offered atmosphere so vicious as to destroy even tire sidewalls and windscreen gasketing in short order.

A dealer may be acting a tad greedy when pushing for replacement at a mere 60% of recommended interval.

Or ... may have 'local' knowledge that some of the many OTHER mounts they service have been seeing earlier belt failures than had been expected.