C4 B78 Picasso 2.0 Auxiliary Belt failure.

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onthecut
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C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by onthecut »

Having done just 10k miles since replacing both belts and all the tensioners, when i got a 'stop at once' warning for battery charge failure, I assumed it must be an electrics issue. Being on a significantly busy and dangerous road, decided to keep going. Made it home ---- so if nothing else, have established a good condition, well charged battery has at least an hour and a quarters reserve in it -- and there was enough left for a restart.

Was significantly surprised to find it was the belt that had given out. It was pleasing to note that both belt covers had done their job -- nothing had been ingested into the cam belt and the outer cover had saved the crank sensor / harness from being lashed by the broken belt. What does concern me is that I really couldn't see any definitive reason for the failure. It seemed as though there may have ben a little notchiness in the smaller tensioner, but it might be my imagination (it was fitted new / Gates). No sign of play or roughness in the alternator or air con pulleys and no apparent issue with the crank pulley. I may just have been unlucky and had a duff new belt (Dayco). One thing I did note however is that the replacement Gates belt I have fitted was specifically marked for the stop start system, whereas the failed belt wasn't. Shouildn't have been a factor anyway, as I have it permanently off.

I did see somewhere that the tensioner pulley had been subject to a revision around 2015 ish -- anyone know why ? I would have thought that by now any quality aftermarket piece would reflect the later spec. Main lesson is that for the few seconds it takes, when doing the underbonnet checks, have a look at the belt for any unusual marking or fraying at the edges -- might just save you considerable inconvenience. Worth noting also that it was two or three restarts before the stop warning disappeared off the dash, even though it was putting out charge from the first start.

Mike.
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CitroJim
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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by CitroJim »

Gosh Mike, that's a very short life for a belt... Dayco are usually OK...

Good advice to check every time you look under the bonnet. I wonder if, as used to happen a lot with some Xantias, one of the tensioner axles was broken or bent which would cause the belt to run off-centre (out of true), ride a tooth out and wear very quickly...

Any off-centre running can usually be seen by eye under a bright light..

Thank goodness the covers did their job. I've seen the resulting carnage when they haven't and it's never a pretty sight...

Even though you don't use stop-start it might be a plan to use the belt specifically recommended in any case. I do wonder, thinking about it, if the stop-start specification belt is under much more tension than the standard one and the use of a standard one with the stop-start tensioners put too much stress on the belt? Just a thought, I may be talking out of my...
Jim

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MattBLancs
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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by MattBLancs »

Do some "start-stop" setups not replace the alternator with a combined "starter-charger" unit?

In which case that belt would be used to start the engine each time - would imagine it was a more substantial item than a normal auxiliary belt in that scenario.



Note also that a visual inspection from above is better than nothing but gives a surprisingly limited view on the belt condition:

viewtopic.php?p=774112#p774112

This looked pretty good from above, maybe a touch glazed but nothing like as bad as the view from below!
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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by wheeler »

MattBLancs wrote: 25 Dec 2023, 18:19 Do some "start-stop" setups not replace the alternator with a combined "starter-charger" unit?
Yes some do, the first C3 with S-S used a reversible alternator & had no starter motor.
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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by CitroJim »

MattBLancs wrote: 25 Dec 2023, 18:19 Note also that a visual inspection from above is better than nothing but gives a surprisingly limited view on the belt condition:

viewtopic.php?p=774112#p774112

Gosh Matt! That one was hanging on by a thread :shock: :lol: You can get a good idea of how true a belt is running from a top check though, after too many Xantias I still do that by default on all mine...
Jim

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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by onthecut »

Interesting thought about the added tension for a stop start belt. There are two tensioners fitted, with the reverse direction one being noticeably chunkier in the body than the standard piece -- so presumably a stronger spring. The 2.0 has both a starter motor and the Dynastart set up --- motor for 'key' starts; the other for stop start. (Be interesting to know if you can spoof the alternator to start it anyway should the motor unexpectedly give out).
With regard to checking the belt, a top view is all you get as the previously mentioned lower cover extends a fair way up, plus you would have to be removing the arch liner to see much, anyway. We used to have a 307 that gradually ate belts, but that gave fair warning as the belt gradually became narrower :-)

Mike.
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Re: C4 B78 Picasso 2.0 Auxiliary Belt failure.

Post by MattBLancs »

Interesting there's two starting methods then,

Guess the dynastart type unit might struggle with a stiff, stone cold engine, thick oil, etc start from cold, but is happy with everything warmed and listened up!