Timing belt failure - thankyou merc. Engineers.

HERBIEMERCMAN

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hi everyone, it amazes me how many car owners ruin their engines due to ignorance of the rubber timing belt failure, smashing the pistons and valve gear on their car.

also how many garages just change the belt ? as unless you check and replace the water pump and belt tensioner, then a new belt can be a waste of time, if water gets onto the belt it will slip out of sink with the crank timing, or if the tensioner allows the belt to come loose it will also get out of sink, leading to total engine failure.

i do not know how many merc. models have the duplex chain drive as my
e-300 has.

all the old ford transits with rear wheel drive have collapsable push rods.

new front wheel drives have the belt drive. a friend of mine who works in engine recon told me that much of their work comes from belt failure.

as an engineer i find it sad that the automotive designers can live with knowing that the average motorist is not aware of the consequences of belt failure and the very expensive consequences.

my brother has a 500 bhp supra, he said i have only done 12,000 miles in the past 5 yrs, so my belt should be ok ? normally the supra belts are 50,000 miles, but he could not appreciate the 5 yr threshold, i explained that rubber has an age reversion, and compresion set, and in un used conditions will fatigue and fail. failure on his engine would be circa £5,000.

has anyone seen any adverts warning car owners about the consequences of belt failure ? i have not, i wonder why ? herbiemercman.
 

Alex Crow

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mercedes, you will be pleased to hear, do not and have never used toothed timing belts.
i am told that in the last decade or so several manufacturers have reverted to chains and gears for some of their engines.
 

MarkF

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My company Vactra 2.2SRi had a chain and I still managed to snap it.
£3,500 damage, new block full engine rebuild.
When I looked at the chain my push bike chain was bigger.
 

rf065

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Not all engines will suffer damage if the timing belt slips or breaks. Engines are classed in two catagories, "Interference Engines" and "Non-interference Engines"

Only in an interference engine can damage occur.

Russ
 
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HERBIEMERCMAN

HERBIEMERCMAN

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hi russ, i know exactly what you mean, but how do you find out what type of engine a car has ? herbiemercman.
 

rf065

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Juddian

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I've had many cars over the years with cambelts, the only failure i've had was some 25 or more years ago on a Volvo 244, no problem non interference engine, and a simple replacement as the belt and pulleys were marked up already, couldn't have been easier, probably half an hours work.

The above was my own fault entirely i hadn't had the car for long and had neglected to replace the belt.....imagine the job involved if that had been a timing chain breaking though, just the dismantling a retiming alone would have been hours, if possible without a timing set.

If you research your car before purchase then a cam belt engine is easier to maintain and keep an eye on that a timing belt can ever be, often it's only the case of undoing a few 8/10mm bolts and slipping the cover off to inspect the thing, and seldom do they break before their time on proper cars...i don't include any FWD car here, as not only are they a PITA to even check a cambelt, they really don't qualify as proper cars anyway..;)

My last Toyota (landcruiser) was a 1 hour replacement at the dealer (cost me a ton including the parts) and my present Toyota pick up is the same timescale, but the replacement i believe is now recommended at 90K miles, though i wouldn't dream of leaving it that long.

Whats the worse to have on a neglected car i don't know....possible snapping cambelt or possible worn chain guides allowing slippage and or breakage.
 

Alex M Grieve

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An unpublished advantage of changing

I had a 1992 Toyota Carina 2L 16 valve petrol car. Bought it 3 years old with 18,000 but quickly put on 1,000 miles per week.

I was getting 36 mpg when I changed the cam belt @ 50,000. I was amazed to see an improvement to 43 mpg thereafter - better than the equivalent diesel car of the day.

So it is not merely good to replace to prevent failure - it can bring a positive benefit too.
 

EireJames

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As above chains aren't 100% either, on VR6s they need doing above 100K, not easy or cheap. I had a Celics SS2 a few cars back, non interference engine, confidence inspiring :)
 

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Early 126 cars had a single chain and a mod was brought out ½ way through its life, the same on other MBs of the same era. I see that they have gone back to a single on some of the diesels from 06 on,,and they have been braking
 

type49

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Not all engines will suffer damage if the timing belt slips or breaks. Engines are classed in two catagories, "Interference Engines" and "Non-interference Engines"

Only in an interference engine can damage occur.

Russ

Not many modern engines left that are non interference.
 

type49

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I hear what you're saying about the cambelt problem but surely this is just part of motoring in general. You know you have to check your oil, lights, tyre pressures etc etc at certain times/mileage - you usually have about 60000 miles to sought out your cambelt. If you don't bother after driving more than twice round the world, is it someone elses fault if it breaks??
 

Alex Crow

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Early 126 cars had a single chain and a mod was brought out ½ way through its life, the same on other MBs of the same era. I see that they have gone back to a single on some of the diesels from 06 on,,and they have been braking

i don't think any 126s had a single changed to a double - you may be thinking of the 124. the 103 series engines always had a single chain in 260 and 300 format, but were absolutely fine. i know a 126 300se with 500k mls on the clock that has never had the head off or any timing chain/gear/rail/tensioner work whatsoever. the 102 series engines however were modded to a duplex design around 1987 or somewhere thereabouts in 201 and 124 chassis. although the 102 engines closely resembled their 6 cylinder bigger brothers, they suffered major chain and gear/sprocket wear in single row guise. back when i started with MB in 1995 we changed many chains and tensioners, often with cam sprocket as well - they wore terribly. i can`t sing the praises of that 103 engine`s single row chain highly enough though.
 

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I hear what you're saying about the cambelt problem but surely this is just part of motoring in general. You know you have to check your oil, lights, tyre pressures etc etc at certain times/mileage - you usually have about 60000 miles to sought out your cambelt. If you don't bother after driving more than twice round the world, is it someone elses fault if it breaks??

For what it cost I change my V70R belt at ½ the mileage at every 40K,,but its only been 70k so far, so only had the 1
 

rf065

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Not many modern engines left that are non interference.

Not so sure about that, if you follow the earlier link to the US site, it is still about 50:50.

Russ
 
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HERBIEMERCMAN

HERBIEMERCMAN

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your getting me worried. i was under the impression that the duplex chain system was bomb proof. my merc has 192,000 on the clock and the original chain.

my father had a jag and the chain used to rattle, he said it was the hydraulic chain tensioner and got it fixed.

he also planted the seed in me that long before a chain breaks you get lots of warning with the rattleing noise. is this true ? herbiemercman.
 

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my merc has 192,000 on the clock and the original chain..

is that a 606 300 diesel? don`t worry, i know one thats done nearly 500,000 mls! never any problems with these engine`s timing chain, gears, guides or tensioner.
 

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...... he also planted the seed in me that long before a chain breaks you get lots of warning with the rattleing noise. is this true ? herbiemercman.

Generally correct. I haven't seen any chains break without due warning. As a Nissan dealer for many years, we had a period - late 1970's - when timing chains used by Nissan in their Oz manufacturing plant were of inferior quality and rattled badly. We were changing them quite regularly at low mileage. We found that it was quite a simple job if we "broke" the chain, connected a new broken chain to the end of the old one and wound it through. Then used a connecting link to join up the new chain in place. Of course there were a few tricks in it but we were able to replace a chain in about 30 mins versus quite a few hours the normal way. This, of course, was only "do-able" if the giudes and tensioner were serviceable. Saved our customers big time.
 

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Generally correct. I haven't seen any chains break without due warning. As a Nissan dealer for many years, we had a period - late 1970's - when timing chains used by Nissan in their Oz manufacturing plant were of inferior quality and rattled badly. We were changing them quite regularly at low mileage. We found that it was quite a simple job if we "broke" the chain, connected a new broken chain to the end of the old one and wound it through. Then used a connecting link to join up the new chain in place. Of course there were a few tricks in it but we were able to replace a chain in about 30 mins versus quite a few hours the normal way. This, of course, was only "do-able" if the giudes and tensioner were serviceable. Saved our customers big time.

The same technique is used on MB chains,,and this does speed the process up.

I normally say that the teeth on the cam wheels should be looked at after say 140k miles,,if the are sharp with no flat on the top of the teeth, then they should be replaced as there is the danger of the chain riding a tooth.

For wear in the chain,, if the engine is put onto its timing marks, then the max at the camshafts should be no more than 3 mm and this is on the average 100 link chain
 

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