More on cambelts
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JohnD
- (Donor 2022)
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More on cambelts
For twelve years our 'stable' has consisted of four XUD's - a BX, two P205's and a Xantia. Putting on new cambelts has been no problem because of the automatic tensioner, but now, our vehicles have changed. I've still got the Xantia, but also a TUD5, a DW8 and a HDI. Haynes emphasizes the importance of getting belt tension correct by using an electronic tool. Does anybody know of a modestly priced one for DIY? Is it really necessary to get the tension so accurate? Looking at the XUD setup, I can't believe that the automatic tensioner exerted the same pressure at ten years old as it did when it was new. I'd welcome some opinions.
John -
As you know the belt manufacturers have to follow stringent international standards, to ensure the belt quality. I think the tensioning requirements on newer engine types are due to the fact of cambelt failures on the older engine types.
Car manufacturers are simply trying to narrow in the way these belts must be tensioned, to ensure a safe service life on the belts.
Lots of cambelts fails due to incorrect tensioning, and sometimes even sloppy tensioning procedures given from engine manufacturers. Even from factory a new engine may have an incorrect tensioned cambelt - the only sane explanation of new engines premature breakdowns.
So - I think you agree it's about time the ever so important cambelt gets the precison work procedures it really needs to ensure safe engine run.
Getting a DIY tool at hand is simply a question of time. Once these are common or garden in any garage, these will "flow" out the market for all. Simple sales marketing stuff.
As you know the belt manufacturers have to follow stringent international standards, to ensure the belt quality. I think the tensioning requirements on newer engine types are due to the fact of cambelt failures on the older engine types.
Car manufacturers are simply trying to narrow in the way these belts must be tensioned, to ensure a safe service life on the belts.
Lots of cambelts fails due to incorrect tensioning, and sometimes even sloppy tensioning procedures given from engine manufacturers. Even from factory a new engine may have an incorrect tensioned cambelt - the only sane explanation of new engines premature breakdowns.
So - I think you agree it's about time the ever so important cambelt gets the precison work procedures it really needs to ensure safe engine run.
Getting a DIY tool at hand is simply a question of time. Once these are common or garden in any garage, these will "flow" out the market for all. Simple sales marketing stuff.
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Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
I would expect the automatic tensioner to be very close to its new spec. even at ten years, the spring only has to put the initial tension on then its locked up and never moves for many thousands of miles.
Think what your valve springs are having to put up with day in day out and you can forget all about the tensioner springs condition, because it should still be like new as far as resiliance is concerned.
Dave
Think what your valve springs are having to put up with day in day out and you can forget all about the tensioner springs condition, because it should still be like new as far as resiliance is concerned.
Dave
John,
As you would no doubt be aware, I have made a bit of a study on these things (cambelts) over the years, mainly due to the phobia a lot of Cit owners have about them, and discovered that a lot of myths surrounded them. The trade were never going to dispel these myths for a few reasons not the least of which was that there was big money to be made by keeping the myths flowing. The mythical tension tester was a good case in point; I asked on a board in Australia, (inhabited by several Froggy mechanics & mostly enthusiasts) if anyone had seen one & could they send me a photo of it. Response:- "What's one of those."
I then asked the same question on a few UK boards & did have one guy send me photos. The rest usually responded that they knew their repairers had one (based on what they had been told), & they would ask to see it. None ever got back, but one guy was curious enough to start asking around all over the UK & discovered that they either; didn't have one, it was broken, nobody knew how to use it, it had been lent out but never returned, they never use it, they ordered one but when it didn't arrive they carried on & found they didn't need it in the first place. I was then contacted by someone who had seen one early in the life of the BX & who discovered that on a BX 16V it won't fit with the engine in-situ and if just the mounts are loosened & the engine swung from a hoist, a possibility that due to space limitations, possibly wouldn't measure accurately anyway. Used when the engine is out on a bench is an entirely different story.
Up to this point, the "recommended" or "standard" fee seemed to be 300 pounds to do the entire job or 180 just to "run the tension checker over it" if you did the job yourself. This was a lively little earner for the more unethical operators because it meant that the 180 figure when it was analysed, was exactly what they should have charged to do the complete job in the first place (3.6 hours @ 45 an hour plus 18.50 for a belt.) and they didn't have to get their hands dirty.
Even using the "tensioner tool" there were still reports of premature failures and investigations into these showed a few common denominators; brand of belt being one. Dayco were proven to be the most reliable apart from getting involved with what is referred to as "competition" belts. This was apparently caused by a slight profile problem in some brands (which will remain nameless for obvious reasons.)
We then struck an interesting one; a guy who claimed he couldn't get his belt tension to adjust properly. We eventually got it sorted but with the time difference it was difficult (me sitting here at 8 am on a 25 dgree morning asking him to check things & being told it's 10 pm -5 and a foot of snow is covering the car[8D] but eventually this opened another can of worms that answered a lot of questions;
In troubleshooting this one, it was found that (in the instance of the BX 16V motor) a sequence in doing the job was far more important than some fancy tool that these guys didn't have or use, it went like this:
Fit belt (using the marking of the teeth and/or the locking pins) and at the same time replace the pump which is low cost throwaway type, and tensioners if necessary.
Adjust the RH tensioner to its maximum position but it hadn't to exceed a specific tension, however more often than not, it didn't make the designated tension but that was no worry.
Adjust the LH tensioner, but *most important!!!* the tensioner had to be rotated anti-clockwise. WHY??? Think about it; if adjusted in the clockwise direction, it will bear down on the belt in an entirely different position thereby lengthening the belt on one run whilst correspondingly shortening it on the other side of the tensioner.
What effect does this have?? It means that to then get the belt tension correct, excessive pressure needs to be applied to the LH tensioner so that the applicable amount of flex in the belt (45 degrees between thumb & forefinger) at the presribed section is attained; what happens in this case is that in the other section, the tension is way over what it should be & this is what can cause the premature failures. All the tension checkers in the world cannot test for this problem; it is down to the guy doing the job.
It was then stated by a couple of ex Cit mechanics who were at service agents when these cars were current & a few of these testers were around, that standard practice was to use the tensioner & then do the thumb & forefinger 45 degree test. If this didn't check out, then they adjusted using the belt twisting method until the 45 degrees was attained; in these cases, why use the tester in the first place?? It all gets back to what is referred to in the "Trade" as good workshop practices.
Alan S
As you would no doubt be aware, I have made a bit of a study on these things (cambelts) over the years, mainly due to the phobia a lot of Cit owners have about them, and discovered that a lot of myths surrounded them. The trade were never going to dispel these myths for a few reasons not the least of which was that there was big money to be made by keeping the myths flowing. The mythical tension tester was a good case in point; I asked on a board in Australia, (inhabited by several Froggy mechanics & mostly enthusiasts) if anyone had seen one & could they send me a photo of it. Response:- "What's one of those."
I then asked the same question on a few UK boards & did have one guy send me photos. The rest usually responded that they knew their repairers had one (based on what they had been told), & they would ask to see it. None ever got back, but one guy was curious enough to start asking around all over the UK & discovered that they either; didn't have one, it was broken, nobody knew how to use it, it had been lent out but never returned, they never use it, they ordered one but when it didn't arrive they carried on & found they didn't need it in the first place. I was then contacted by someone who had seen one early in the life of the BX & who discovered that on a BX 16V it won't fit with the engine in-situ and if just the mounts are loosened & the engine swung from a hoist, a possibility that due to space limitations, possibly wouldn't measure accurately anyway. Used when the engine is out on a bench is an entirely different story.
Up to this point, the "recommended" or "standard" fee seemed to be 300 pounds to do the entire job or 180 just to "run the tension checker over it" if you did the job yourself. This was a lively little earner for the more unethical operators because it meant that the 180 figure when it was analysed, was exactly what they should have charged to do the complete job in the first place (3.6 hours @ 45 an hour plus 18.50 for a belt.) and they didn't have to get their hands dirty.
Even using the "tensioner tool" there were still reports of premature failures and investigations into these showed a few common denominators; brand of belt being one. Dayco were proven to be the most reliable apart from getting involved with what is referred to as "competition" belts. This was apparently caused by a slight profile problem in some brands (which will remain nameless for obvious reasons.)
We then struck an interesting one; a guy who claimed he couldn't get his belt tension to adjust properly. We eventually got it sorted but with the time difference it was difficult (me sitting here at 8 am on a 25 dgree morning asking him to check things & being told it's 10 pm -5 and a foot of snow is covering the car[8D] but eventually this opened another can of worms that answered a lot of questions;
In troubleshooting this one, it was found that (in the instance of the BX 16V motor) a sequence in doing the job was far more important than some fancy tool that these guys didn't have or use, it went like this:
Fit belt (using the marking of the teeth and/or the locking pins) and at the same time replace the pump which is low cost throwaway type, and tensioners if necessary.
Adjust the RH tensioner to its maximum position but it hadn't to exceed a specific tension, however more often than not, it didn't make the designated tension but that was no worry.
Adjust the LH tensioner, but *most important!!!* the tensioner had to be rotated anti-clockwise. WHY??? Think about it; if adjusted in the clockwise direction, it will bear down on the belt in an entirely different position thereby lengthening the belt on one run whilst correspondingly shortening it on the other side of the tensioner.
What effect does this have?? It means that to then get the belt tension correct, excessive pressure needs to be applied to the LH tensioner so that the applicable amount of flex in the belt (45 degrees between thumb & forefinger) at the presribed section is attained; what happens in this case is that in the other section, the tension is way over what it should be & this is what can cause the premature failures. All the tension checkers in the world cannot test for this problem; it is down to the guy doing the job.
It was then stated by a couple of ex Cit mechanics who were at service agents when these cars were current & a few of these testers were around, that standard practice was to use the tensioner & then do the thumb & forefinger 45 degree test. If this didn't check out, then they adjusted using the belt twisting method until the 45 degrees was attained; in these cases, why use the tester in the first place?? It all gets back to what is referred to in the "Trade" as good workshop practices.
Alan S
My 2.0 sxi belt broke at 47,000 miles from new causing the usual very expensive damage. I fitted the new one and adjusted the tension by the "90 degree method" i.e., tighten it so that the longest run can just be turned by 90 degrees. The new belt has done 44,000 miles without a problem. Oops must get around to changing it!