When it comes to timing belts are engine manufacturers lazy?
Discussion
Almost finished changing the cambelt on a Jaguar 2009 3.0D. I was just re-assembling yesterday when I ran out of daylight.
It's been a pig of a job (weather hasn't helped). The amount of stuff that had to be removed to get the covers off in this engine bay is insane.
And to top it off, the old belt, whilst it is original, looks to be in great condition. Probably would have lasted another 100k and 10 years I expect.
I know many on here would only choose chains, but belts do have their place. They are cheaper, quieter, lighter, don't need lubricating, no complicated hydraulic tensions meaning it's not loose on start-up. Probably other benefits also.
This has got me thinking, have the engine designers just been lazy when it comes to timing belts?
Why don't they have two skinnier belts instead of one chunky one?
And a convenient little inspection window?
That way, you could ignore the service interval, and just periodically check that both belts are still there.
You would no doubt hear the old belt flapping around so you couldn't ignore it too long. You'd probably want some baffles to prevent the broken belt form taking out the working belt.
Hell, for pennies you could have a couple of sensors that detects when a belt is missing and put you into limp-mode.
The above seems quite straight forward, negligible cost, and would massively reduce maintenance requirements and result in fewer blown engines where services have been ignored.
Usually when something seems obvious and a no brainier there's something I'm missing, but not sure what it is in this case.
School me please.
It's been a pig of a job (weather hasn't helped). The amount of stuff that had to be removed to get the covers off in this engine bay is insane.
And to top it off, the old belt, whilst it is original, looks to be in great condition. Probably would have lasted another 100k and 10 years I expect.
I know many on here would only choose chains, but belts do have their place. They are cheaper, quieter, lighter, don't need lubricating, no complicated hydraulic tensions meaning it's not loose on start-up. Probably other benefits also.
This has got me thinking, have the engine designers just been lazy when it comes to timing belts?
Why don't they have two skinnier belts instead of one chunky one?
And a convenient little inspection window?
That way, you could ignore the service interval, and just periodically check that both belts are still there.
You would no doubt hear the old belt flapping around so you couldn't ignore it too long. You'd probably want some baffles to prevent the broken belt form taking out the working belt.
Hell, for pennies you could have a couple of sensors that detects when a belt is missing and put you into limp-mode.
The above seems quite straight forward, negligible cost, and would massively reduce maintenance requirements and result in fewer blown engines where services have been ignored.
Usually when something seems obvious and a no brainier there's something I'm missing, but not sure what it is in this case.
School me please.
2 belts would be pointless. One belt fails, wraps itself in the other...boom
A bit like the old Ford 1.8tdi....and on later models, Ford had the genius idea of running one of the belts in oil. Which then failed far too early, and often people didn't realise there as a belt in there to be changed. As running a belt in oil would have been stupid.
A bit like the old Ford 1.8tdi....and on later models, Ford had the genius idea of running one of the belts in oil. Which then failed far too early, and often people didn't realise there as a belt in there to be changed. As running a belt in oil would have been stupid.
Often a removed belt will 'look fine', but you just never know. Besides it is actually often the tensioner that fails and then takes the belt out with it. This is why it's always essential to replace the tensioner. Sometimes it can be the water pump instead.
Twin belts are sometimes seen but for the ancillaries...I've only seen the set up on some old American engines. Using twin belts for the timing would extend the length of the engine, add complications for tensioning and then protecting the other belt in case of failure. Moreover it will increase the cost. Remember in automotive, cost is everything.
Reminds me something I saw once on our old Uni race car, a sharp piece of debris got into the timing cover and sliced the belt all along its length. The car completed the race on effectively two belts.
Twin belts are sometimes seen but for the ancillaries...I've only seen the set up on some old American engines. Using twin belts for the timing would extend the length of the engine, add complications for tensioning and then protecting the other belt in case of failure. Moreover it will increase the cost. Remember in automotive, cost is everything.
Reminds me something I saw once on our old Uni race car, a sharp piece of debris got into the timing cover and sliced the belt all along its length. The car completed the race on effectively two belts.
HJG said:
Often a removed belt will 'look fine', but you just never know. Besides it is actually often the tensioner that fails and then takes the belt out with it. This is why it's always essential to replace the tensioner. Sometimes it can be the water pump instead.
Twin belts are sometimes seen but for the ancillaries...I've only seen the set up on some old American engines. Using twin belts for the timing would extend the length of the engine, add complications for tensioning and then protecting the other belt in case of failure. Moreover it will increase the cost. Remember in automotive, cost is everything.
Reminds me something I saw once on our old Uni race car, a sharp piece of debris got into the timing cover and sliced the belt all along its length. The car completed the race on effectively two belts.
Twin belts are sometimes seen but for the ancillaries...I've only seen the set up on some old American engines. Using twin belts for the timing would extend the length of the engine, add complications for tensioning and then protecting the other belt in case of failure. Moreover it will increase the cost. Remember in automotive, cost is everything.
Reminds me something I saw once on our old Uni race car, a sharp piece of debris got into the timing cover and sliced the belt all along its length. The car completed the race on effectively two belts.
Reminds me of the old bodge if you didn’t have the locking tools, running the engine and using a Stanley knife to cut the belt in half along it’s length , stopping the engine slacking the tensioner and removing the outer half fitting the new belt then cutting the remaining bit of the old belt !! What?? Well it worked!!
montyjohn said:
Why don't they have two skinnier belts instead of one chunky one?
And a convenient little inspection window?
Don't they often break as the a tensioner or water pump fails?And a convenient little inspection window?
What irks me is VAG cars where in the UK they insist they must be changed at 5yrs regardless of mileage.
To me, a better idea would be to ensure the belts are non-interference, so one breaking isn't catastrophic. I had a Cavalier rep-mobile years ago that broke its belt three times. Bit of a pain (especially the time where it left me in lane 3 of the M62), but easily fixed.
Ivan stewart said:
Reminds me of the old bodge if you didn’t have the locking tools, running the engine and using a Stanley knife to cut the belt in half along it’s length , stopping the engine slacking the tensioner and removing the outer half fitting the new belt then cutting the remaining bit of the old belt !! What?? Well it worked!!
That's genius, full marks!stevieturbo said:
2 belts would be pointless. One belt fails, wraps itself in the other...boom
As mentioned in my original post, a simple set of baffles in-between would protect the remaining belt. I think this could be easily overcome.MC Bodge said:
Cars that need new timing belts are typically well out of warranty.
Do we not think manufacturers care about long term reputation for reliability etc. If buying a new car, resale price is a key factor so I expect it would translate to more sales if the engines we're regarded as being bomb proofIvan stewart said:
running the engine and using a Stanley knife to cut the belt in half along it’s length
I believe this is called the Russian technique. It's great for older engines, newer ones however, are so tight in the engine bay that you have to remove too much that I believe the engine wouldn't run. Edited by montyjohn on Tuesday 14th December 11:26
Sheepshanks said:
Don't they often break as the a tensioner or water pump fails?
To me, a better idea would be to ensure the belts are non-interference, so one breaking isn't catastrophic.
Possibly, although on my XF the water pump is accessory belt driven. I changed it anyway but probably wasn't required. I get the impression that idlers and tensionsers typically fail in a non catastrophic way. Bearing grind etc. But could be wrong on this.To me, a better idea would be to ensure the belts are non-interference, so one breaking isn't catastrophic.
I think the issue with non-interference engines you are limiting your engine to small valve lift and/or low compression with is a hit on performance and efficiency. The above can be limited with deep pockets on pistons, but I suspect for high compression ratios, you can't afford those deep pockets.
Edited by montyjohn on Tuesday 14th December 11:51
They don't care beyond warranty.
Lots of engines now have "wet belts" despite them being an absolute pain in the arse with common failures before their rated intervals and high invasive costs to replace.
The 1.2 pure air pug engine, fords ecoboost 1.0, think the latest ford panther also uses a wet belt in things like transits.
Lots of dead engines from them
Lots of engines now have "wet belts" despite them being an absolute pain in the arse with common failures before their rated intervals and high invasive costs to replace.
The 1.2 pure air pug engine, fords ecoboost 1.0, think the latest ford panther also uses a wet belt in things like transits.
Lots of dead engines from them
The two belt thing won't work without complete separation - it is quite common on some engines for the aux belt to take out the cambelt via the waterpump.
Overall the problem is this - there are two modes of belt failure.
Mode 1 is mechanical failure of the belt pulleys. Happens all the time in Alfa 24v V6s. The tensioner bearing wears, and the belt wanders, generally into one of the covers or block. Over 1000 miles or so, it wears itself down to nothing and snaps. Loads of warning, you just need to pull back the cover and check for wandering belts.
Mode 2 is just the belt snaps. This is how 4 cylinder Alfas die. The belt looks fine, tracks fine, and just snaps. It's down to the tension the belt runs at, the crazy contortions it makes as it rotates and the width of the belt. You have no warning, other than your calendar.
Changing a 24 valve V6 belt is, er, challenging.
Overall the problem is this - there are two modes of belt failure.
Mode 1 is mechanical failure of the belt pulleys. Happens all the time in Alfa 24v V6s. The tensioner bearing wears, and the belt wanders, generally into one of the covers or block. Over 1000 miles or so, it wears itself down to nothing and snaps. Loads of warning, you just need to pull back the cover and check for wandering belts.
Mode 2 is just the belt snaps. This is how 4 cylinder Alfas die. The belt looks fine, tracks fine, and just snaps. It's down to the tension the belt runs at, the crazy contortions it makes as it rotates and the width of the belt. You have no warning, other than your calendar.
Changing a 24 valve V6 belt is, er, challenging.
archie456 said:
Ivan stewart said:
Reminds me of the old bodge if you didn’t have the locking tools, running the engine and using a Stanley knife to cut the belt in half along it’s length , stopping the engine slacking the tensioner and removing the outer half fitting the new belt then cutting the remaining bit of the old belt !! What?? Well it worked!!
That's genius, full marks!The water pump & idlers probably cause at least as many failures as the belts themselves, so they aren't being replaced doing it that way.
bungz said:
They don't care beyond warranty.
Lots of engines now have "wet belts" despite them being an absolute pain in the arse with common failures before their rated intervals and high invasive costs to replace.
The 1.2 pure air pug engine, fords ecoboost 1.0, think the latest ford panther also uses a wet belt in things like transits.
Lots of dead engines from them
Yes but apparently they are blaming failures on the wrong oil they recon Lots of engines now have "wet belts" despite them being an absolute pain in the arse with common failures before their rated intervals and high invasive costs to replace.
The 1.2 pure air pug engine, fords ecoboost 1.0, think the latest ford panther also uses a wet belt in things like transits.
Lots of dead engines from them
some additives attack the material the belt is made of !!
With twin toothed belts, I think the big problem would be that the belts would have a slightly different length, due to manufacturing tolerances so the tension would be higher in one belt.
This would lead to premature weakening of this belt as it would be doing most of the work, so to speak.
It would only work if you doubled up on the existing belt width.
This would lead to premature weakening of this belt as it would be doing most of the work, so to speak.
It would only work if you doubled up on the existing belt width.
Sheepshanks said:
Don't they often break as the a tensioner or water pump fails?
What irks me is VAG cars where in the UK they insist they must be changed at 5yrs regardless of mileage.
To me, a better idea would be to ensure the belts are non-interference, so one breaking isn't catastrophic. I had a Cavalier rep-mobile years ago that broke its belt three times. Bit of a pain (especially the time where it left me in lane 3 of the M62), but easily fixed.
To do you need a lower compression engine so not really practical especially on a dieselWhat irks me is VAG cars where in the UK they insist they must be changed at 5yrs regardless of mileage.
To me, a better idea would be to ensure the belts are non-interference, so one breaking isn't catastrophic. I had a Cavalier rep-mobile years ago that broke its belt three times. Bit of a pain (especially the time where it left me in lane 3 of the M62), but easily fixed.
Apart from Volvo 2.0 litre engines as fitted to 240 series cars, the easiest timing belt i've changed is the Toyota 3.0 D4D, all belts should be like this, driving only the camshafts.
https://www.youtube.com/watch?v=HNNP66BbUIw
https://www.youtube.com/watch?v=HNNP66BbUIw
Sheepshanks said:
Don't they often break as the a tensioner or water pump fails?
What irks me is VAG cars where in the UK they insist they must be changed at 5yrs regardless of mileage.
Those two lines go hand in hand. The water pumps on VWs are the weak point. The originals had a plastic impeller an interference fit on the brass shaft and often due to lack of antifreeze the the coolant would freeze up in winter. Try starting the engine and the water pump turns but the impeller doesn't as the plastic strips. Often not noticed until the engine starts overheating. Replacement pumps have steel impellers pressed on which can also fail if no antifreeze and the coolant is solid but this time the teeth on the belt are stripped!What irks me is VAG cars where in the UK they insist they must be changed at 5yrs regardless of mileage.
I always recommend replacing the belt on TDIs every 40,000 miles or 4 years having seen too many failures.
Smint said:
Apart from Volvo 2.0 litre engines as fitted to 240 series cars, the easiest timing belt i've changed is the Toyota 3.0 D4D, all belts should be like this, driving only the camshafts.
https://www.youtube.com/watch?v=HNNP66BbUIw
My old man had the local motor factors bring him a new belt to where he had broken down, and he fitted the new belt and carried on his way. Mk2 Transit with a Pinto.https://www.youtube.com/watch?v=HNNP66BbUIw
I was watching a YouTube video yesterday where they were sorting various small oil leaks on a Cummins diesel engine on a pick up that was approaching 1 million miles , all the timing system was thick cut gears which showed no significant wear l , no belts or chains or other nonsense , can't help thinking that's why it was still running so well after so many miles.
Compare that to many cars that require an engine out job to replace the belt every 5 years , they could do it if they wanted but they choose not to
Compare that to many cars that require an engine out job to replace the belt every 5 years , they could do it if they wanted but they choose not to
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff