Not servicing a car?

Hmm, I beg to differ just a little ... Done properly - possibly 95% right.

However, I deal in printing machinery, which use a similar assortment of timing belts, moving cams and lubricants under the skin. You can almost gurantee that a perfectly functioning machine if left alone will continue to do so, and only 1% will eventually die horribly due to a belt failure.

However, a machine 'serviced' will run like a dog for a week or so until it settles in and then probably 5% will throw a belt and die horribly within 12 months - because the old belt and tensioners and bearings all got along nicely - a new belt will take on a bearing and then a tensioner because the dynamics are all wrong...

Can scientifically say *why*, it is just *so* - we make far more money out of people who say "full service please" that those who just call us for breakdowns.

We are not talking about photocopiers here. This is cars. if the oil all falls out the engine goes bang, similar for all the water. Car timing belt systems do break and when they do the engine is scrap. Failure to change the plugs on time means the leads and coil packs fail. yes you can ignore the air and fuel filters almost indefinitely on a modern vehicle, but not the oil, water and cam belts, when any of them fail the engine stops often for good.

I don't see why renewing the plugs from time to time should be better than re-setting the plug gap from time to time (on the assumption that the plug is basically OK).

Rob Graham

IIUC the precious metal is a covering which once worn away will give very high wear rates, also the covering of combustion products can lead to a tracking condition, likewise the porcelain outside the engine. There is also a danger of very elderly electrodes falling off, and of course multi electrode plugs cannot be re-gapped. So yes, regapping could prevent the start of tracking due to overhigh voltage, but with some modern plugs lasting 60k - 100k without attention and high grade escort ones doing 30k I think I'll just renew them when specified rather than mess about to save a small amount.

I went on a Champion spark plug course once (about thirty years ago) We were shown that standard plugs noticeably de-grade after less than a thousand miles, and that they are seriously poorly after 6000 miles.

Thing is, most car engines run on petrol or diesel, both of which leave deposits around the engine in time, which degrades the oil. I imagine most printing machinery is electrically powered, and doesn't have the bi-products of combustion to cause potential problems. That's a pretty big factor, I'd guess.

Yup, most of the stuff I own just gets PAT tested & the screws checked for tightness, the only things that get serviced are the IC engines & the chain hoists (& that's a legal requirement, thet get serviced way more regularly than needed to avoid failures)

I can vouch for that , one of my old motorcycles after 2000 miles would always lose power in one cylinder , quick change of the plugs and off you would go again ,

Printing machinery involve lots of ink and chemicals. Quite often a service stripping off layers of dried residuals will cause the machine to run like a pig until the layers have deposited again.

Could it have been the one running wrong polarity on wasted spark?

In the early 80's I went to a Champion event to promote the introduction of copper cored plugs. I was amazed that this was new technology. Having, except for one occassion, only ever had NGKs I thought it was standard.

It explained why that one brand new Champion plug I bought in 1978 wasn't as good as a 2 month old NGK. I didn't have to work out which one it was as there was only the one. Oil change, tappets, new plug and points every 1500 miles, it was a hard short life at 9.5K and occasional overspeed to 12K rpm. Easy to tell that service was due as top speed (=nominal cruise) dropped from 65mph that it did when fresh and crisp to a lame 60mph. When you only have 12bhp it's easy to spot that one has dropped dead. It's way harder to spot that 8 out of 100 is missing.

Your logic and service procedures are both defective.

You have a contradiction "the existing set will run forever" v's "quite often one will throw a tooth". Once one has thrown a tooth the entire existing set is garbage.

In throwing that tooth there will ALWAYS be damage to teeth of other gears that were in mesh with it. The meshed gear teeth take repeated impacts from the skip every time the gap comes round before the press is stopped. The shock from that impact will extend though the whole gear train to the nth mesh. Additionally if they all run in a common oil/grease supply then the fragments can and by sod's law will cause damage to all gears running in that system. You just haven't inspected every flank of every tooth to an adequate standard.

May I suggest you issue a Technical Service Bulletin to reflect that fact and your experience. TSBs are a normal way to change service/repair requirements in light of operational experience.

Pre 2000 Ford Mondeo Diesels had a short cam belt life. Started off at

60K miles pretty much in line with many other auto engine belt drives. Many failed. Ford issued a TSB for 48K mile belt change, upset a lot of fleets as they now had to pay for that belt change. There were still failures in service period so a 2nd TSB was issued for 36K mile belt change interval. Ford sell a full kit of parts some of which are revised, comes with instructions but it's still 36K mile changes.

Everything breaks but only a few industries spend what it takes to know WHEN it will break. Knowing WHEN something will break means the thing gets taken apart and the bit replaced before it breaks. Aero and Nuclear are 2 industries that do this. The car makers simply can't afford to do the analysis, testing and document the service for cars, nor can you for printing presses. They do get close for F1 which is why £40m/pa won't cover it.

Take a Turbofan Aeroengine High Pressure (HP) Turbine Disc. It's not economically possible to make one that won't break, about 60cm diameter, they run 12000rpm, 600°C rim temp, 46MW, with 60 to 70 0.3Kg HP turbine blades hanging off the rim that each produce 14.5 tonnes of CF force (=Dennis Trident Double-Decker Bus). To make one that would never break it would be so heavy that it quite literally would never fly. The finding out as to when it will break cost's £1m's but they can't afford not to do that work.

Sometimes they get it wrong and a part breaks before it's service life is up. 9,186 cycles since new (CSN), with 5,814 cycles remaining for the disk?s 15,000 CSN life limit.

your argument they should stop servicing them and just wait forthem to break - they know they will, that's why it has a 15,000 CSNlimit. "3rd piece of disc found 2,500 feet away" and fortunately missed goingthough an in service plane on the way. The fault was known and arework scheme in place, they just didn't get it into the shop and donequite in time for that one. Result - new Airworthiness Directive, asomewhat higher level document than a TSB.http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgAD.nsf/0/9F7F945887447A6A86257566004E5BB0?OpenDocument

In message , Peter Hill writes

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That reminds me of the time we lost a tooth off the crown wheel on our old 1936 Morris 8 somewhere in Derbyshire when Dad's foot slipped off the clutch. The 30 mile journey home was an embarrassing bump-bump-bump-bump, and the mechanic from the garage next door pushed the car round to their workshop because he was scared of driving it a few yards. ;-)