Megane II intermittent accessory belt break
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Thread: Megane II intermittent accessory belt break

  1. #1
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    Default Megane II intermittent accessory belt break

    broke my accessory belt on 2004 Megane II cabrio. Was suspicious why belt broke the first time but the alternator, the a/c (and clutch), and the idler all spun around nicely with no bearing rumble. So I just replaced it.
    All went well for a few more weeks and then it snapped the new one, but whilst it was at it - the harmonic balancer separated and all electrics stopped.
    Again, all accessories spin nicely as before, no apparent reason for the belt to break or tear the rubber connection in the Harmonic balancer.
    Worst thing is the harmonic balancers seem to be pretty much impossible to find non-genuine or second-hand in regional Qld. I read Laguna with similar engine thread here where poster was quoted over $600 for genuine replacement.
    So, do I buy another Harmonic Balancer (if I can get one), a new a/c compressor and a new alternator to make sure it doesn't happen again (probable cost close to $2K)?.
    Or; do I take a punt the a/c seized (it was a hot day with a/c on flat out) and free'd up when it cooled, replace that and hope that's okay - at the risk of wrecking another belt and H/Bal.
    Or; do I replace the alternator on the off chance it has a dead short that causes it to lock up, but otherwise works ok?
    Do any of these problems/symptoms sound familiar to anyone?

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  2. #2
    1000+ Posts alan moore's Avatar
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    It is quite possible that the compressor is siezing and of course with the electric clutch not powered up it will freewheel fine. Easy enough to power up the clutch and see how hard the compressor is to turn over by hand, which you should be able to do reasonably easily and smoothly.

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    How old was the harmonic balancer? It isn't unknown for them to let go. It may have been wobbly when it first went, then failed when the new belt was installed. After first damaging the belt again to make it difficult to pinpoint the actual cause..........
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    Hi Bluemegan
    Some good suggestions made already to check out.
    IMHO the harmonic ballancer failing is likely the cause not the result. If the outer is coming off the belt runs off line and touches the other parts as it runs.

    How did the belt fail ?? Did it squeel at all when you put the a/c on or at starting ? Did it fall in to strips ? Did the edges get worn away and melted ?

    I have not seen a belt that snapped across even with a siezed compressor.
    Jaahn

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    yes, I can turn the compressor (centre part)and it spins quite easily by hand. And, with clutch not activated, the outer pulley also spins quite well as separate from the inner compressor shaft.

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    Yeah, it's a conundrum alright. When I changed the belt the first time I found it very difficult to fit and I would have noticed if there was any play in the harmonic balancer (well, at least I hope I would have). the second point is that there was an awful burning smell - and smoke coming from the engine when the first belt broke which made me think there was some incredible friction happening to the belt (ie, something seized or stopped). Unfortunately I wasn't driving it the second time, so I'm not sure what happened exactly. The "incident report" was a bit patchy, lol. . I reckon a/c/ or Alt seized again the second time -but with a new and much grippier belt and the engine tried to keep driving the belt and ultimately forced the Harmonic Balancer to tear its rubber mount.

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    Hi Jaahn, I was driving the first time but not the second time - so not sure what happened the second time, only the result! It could well have been smoking the second time(well it must have been cos there are rubber granules from the balancer all over the engine bay), but it happened at highway speed the second time would have happened quickly, dash lights all lit up and then pulled over.
    I was driving the first time, I was driving slowly and then saw dash lights on and smelt burning rubber, no squealing that I remember. I lifted the bonnet, lots of smoke) and left it to cool for a bit. Was dark and only a block and a half from home so limped home.
    The belt broke in much the same way each time, not stripped, edges fine and no real evidence of melting. I'm still trying to find te problem or it will keep costing me money....

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    Hi
    Thanks for the reply. The pulleys fail by the bond between the two halves failing and the inner bit does not drive the outer OR while that happens the outer part slides off to the front out of line. So you can see the possibility of the belt rubbing. There may be lots of ways to fail really after it gets hot and the rubber insert gets soft and less grippy. It is a common problem in lots of brands of cars. Particularly if there is a bit of an oil leak around there to rot the rubber.

    There would be no looseness or play when you put the new belt on as it had cooled down and was stuck on a bit with melted rubber probably.

    I have never seen an alternator that siezed and then turned freely. A short or the like will not stop them turning just burn them out. They only part sieze in my experience when a bearing fails completely and that is obvious after as is the noise beforehand.

    The a/c compressor is usually the same really. They do not sieze up and then go free again, They only sieze from lack of oil and then they stay solid or very tight. I believe you are looking at the wrong things here IMHO.

    The ballancer pulley is the most likely thing if the other rotating items feel to be OK. It is quite possible you would not notice it was faulty as the belt replacement is a bitch of a job down the side and you cannot get a good view of the whole system.
    Good luck Jaahn
    Last edited by jaahn; 18th February 2018 at 11:47 AM.
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    Megane II intermittent accessory belt break-img_20180218_100609.jpgMegane II intermittent accessory belt break-img_20180218_100527.jpgClick image for larger version. 

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    Hi again Jaahn,
    You make a good point but it still doesn't add up to a clean break of the belt. This break is almost identical to the last break. Belt in really good condition.
    I agree, I have never known alternator or a/c compressor to seize and then free up. usually they deteriorate over time and get noisier - if it's bearings, or short out or just seize or something. However, there were none of those symptoms. But there was burning and smoke that tells me the belt was slipping over something stationary. And the harmonic balancer needed to be turning the belt to make that happen - cos if it was stationary, everything would stop turning. I feel the engine was trying to drive something that would not turn.
    My logic is as follows; there are four things on the accessory belt: alternator, a/c compressor, idler wheel and the harmonic balancer. If it was the idler seizing that would just scream and probably not cause it to break straight away as it is on the flat side of the belt, so I discounted that as it spins easily with no noise. If it was the harmonic balancer that stopped, the belt would stop and no smoke. If the harmonic balancer was loose it would show some fraying or belt would have run oddly and showed odd wear pattern.
    That leaves me with just the a/c or alt. Both of these things are known to seize - but they dot usually free up after. That's my dilemma.
    If I go to the expense of replacing the HB and the same thing happens again I am up for the big bucks all over again. So I want to make sure I get it right. I do have to replace the HB anyway, I just don't want to do it twice.
    Is there any way to check a/c compressors or alternators for intermittent failure?

  10. #10
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    The smoke was most likely the inner rubber bonding of the harmonic balancer burning out. I'm with jaahn I think the harmonic balancer is the fault! But this is one of those things that diagnosing without the car is near impossible!

    Also be careful when you change the balancer because you'll need to lock up the crank. I've also seen bits of the rubber from the harmonic balancer (sometimes also the belt) wrap around around crank shaft gear and put the timing out. Resulting in bent valves.
    Good luck!
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    Hi Bluemegane
    Well that is a straight tension break. The only time I have seen a break like that is when something has fallen into the belt and gone between it and a pulley. That put a big stress on the belt and can break the cords. Is there some wire connector, hose, cover or anything that may drop or swing in there and then get out after causing that to happen. A bit way out but ??

    Is it possible the a/c has been overcharged and this is causing a liquid return to the compressor ?

    What motor do you have ? I guess there is a PS pump too.
    Jaahn

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    Thanks Cav91. gotta change the balancer anyway so I guess we will see

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    Jaahn,
    I like both those suggestions. I will see if there is anything floating about down there. However, your a/c thought interests me greatly. The belts have only broken since the a/c was re-charged, and the mechanic wasn't familiar with Renaults and couldn't find one of the a/c valves but said he topped it up and it should be okay??? I thought nothing of it at the time because the a/c worked and in Qld that is an important thing in a car with a glass roof.
    I don't know what overcharged is but can it cause the compressor to lock up?

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    Quote Originally Posted by Bluemegane View Post
    Jaahn,
    I like both those suggestions. I will see if there is anything floating about down there. However, your a/c thought interests me greatly. The belts have only broken since the a/c was re-charged, and the mechanic wasn't familiar with Renaults and couldn't find one of the a/c valves but said he topped it up and it should be okay??? I thought nothing of it at the time because the a/c worked and in Qld that is an important thing in a car with a glass roof.
    I don't know what overcharged is but can it cause the compressor to lock up?
    Hi
    Overcharged is too much refrigerant put into the system. More than the specified quantity.

    I have no experience of it, but in theory the possibility is that instead of gas getting back to the compressor it may be still liquid. That is not compressible so the compressor will not be able to handle it as it cannot compress it. It may be damaged or perhaps just stop dead Never seen it happen but know it can ! Sounds like a good theory here
    Just a quick Google gives this;
    Not only is overcharging your system potentially dangerous, an overcharged system will not function properly and can seriously damage your A/C compressor or other component parts.
    Jaahn
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    Default Hmmmmm :(

    Bluemegane
    Read this from this site;
    https://itstillruns.com/signs-sympto...c-7834056.html

    Signs & Symptoms of an Overcharged AC By MayankJ
    bla bla ---
    Inefficient Cooling. bla bla-----
    Compressor Noise. bla bla-----
    High Pressure Readings. bla bla-----
    Struggling Engine. An AC compressor can draw a significant amount of power from the engine, never more so than when it's trying to push a gallon of coolant through a one-ounce nozzle. This excessive power draw can cause the compressor's drive belt to slip and screech, which generally precedes a loud snap and belt failure. Or, the belt may hang on, and sap power from the engine. In this case, you may end up with a low or fluctuating idle, sluggish acceleration and excessive loss of fuel economy when the AC is running.
    Broken Compressor. This is often the inevitable end result of a chronically overcharged system. The compressor is your AC system's heart, and eventually it's going to respond the same way your heart would if you had chronic high blood pressure. Internal seals will fail, valves will cease to function, the pump will fail and the system will ultimately flatline.

    Jaahn
    PS I also asked a question in the Techies Section for feedback on Overcharge problems.

  16. #16
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    Our Series II Megane (Scenic) recently had an AC compressor partial seizure. We caught it before anything broke (smell plus no AC!!) and the belt was badly damaged.

    New compressor, new belt and pulleys etc and all seems OK.

    Same mechanicals as yours maybe.
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    Thanks to all who replied, all ideas greatly received.
    Managed to get a new Harmonic Balancer from Melbourne as suggested and am in the midst of putting car back together now.
    Had alternator tested ok by local auto elec and that really just leaves the a/c compressor. I bought the car with non functioning a/c so just had it recharged and it was not long after that the belts broke. So I am thinking a/c compressor. When I get it mobile I will take to a/c specialist for checking...
    stay tuned

  18. #18
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    Hi
    Do not start the job untill you are sure you know how to do it. That harmonic ballancer may leave the timing pulley behind it loose so as mentioned already it will be a disaster if the camshaft timing is made incorrect in the process.
    Can any person here say if the bottom timing gear/pulley is keyed to the crankshaft with no free play or does it have a wide keyway or none even ????
    If in doubt you must lock all the shafts to hold it correct as you tighten the HB screw. This has to be done tight then torqued to yield with another angle turn, which is hard to do. There is currently a procedure with photos on here doing the timing belt. Perhaps you should look at your idler pulleys as they crack and fail.
    Gates Timing Belt Kits with STEEL idler pulleys for Renault engines.
    Jaahn
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    Quote Originally Posted by jaahn View Post
    Can any person here say if the bottom timing gear/pulley is keyed to the crankshaft with no free play or does it have a wide keyway or none even ????
    My Scenic I has an F4R 2.0 litre engine, it does not have ANY keys to locate timing belt pulleys on either the crankshaft or the camshafts, and I believe this is common across the Renault engine range. Jaahn (and Cav91 above) are correct, loosening the harmonic balancer pulley, without locking both the crankshaft and camshafts may result in cam timing moving. Also the harm balancer bolt is very tight and the crank aligning pin should not be used to hold it from turning. My method, before loosening the HB bolt, is to rotate the crank until the cams are aligned (cross slot below centreline), insert cam locking plate, insert crank locking pin, hold flywheel positively against rotation (not easy), loosen HB bolt - do not remove any locking pins.

    If you need any more detailed info on the tools, let me know. If you are already aware/experienced in this job, then sorry for trying to teach you how to suck eggs!

    BTW, although at first I thought the "no key" system was stupid, when I realised how it sets up the cams perfectly every time (without needing an after-market vernier timing device), I think it is a good system.

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    New problem, HUGE.
    OMG. Put new Harmonic Balancer back on - no key, so possibly no problems. went on okay, new belt of course. Disconnected a/c so clutch not engage compressor.
    When all hooked up, start car - to an incredible clattering sound. Sounds somewhere between a clanging, scraping, exhaust chuffing and heatsheild rattle all rolled into one.
    OMG
    OMG
    I am halfway to fixing one thing and another descends upon me.
    From research on google the best I can come up with is a dephaser problem. Could it be?
    How so all of a sudden, unless the timing belt has indeed slipped? Possible? unsure, shouldn't have I don't think. Car starts ok, runs a bit rough but sounds dire.
    If timing belt had slipped it wouldn't start so readily I think.
    Getting a bit disillusioned with this car........

  21. #21
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    Sounds like the timing is out. If you are not sure get a Renault mechanic to do it or you could wreck the engine.
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    Quote Originally Posted by Bluemegane View Post
    New problem, HUGE.
    OMG. Put new Harmonic Balancer back on - no key, so possibly no problems. went on okay, new belt of course. Disconnected a/c so clutch not engage compressor.
    You did read Cav91/Fordmans posts about locking the crank and cams…... and followed this advice, Yes??????

    If not,
    Last edited by jo proffi; 24th February 2018 at 05:29 PM.
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  23. #23
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    Quote Originally Posted by Bluemegane View Post
    New problem, HUGE.
    OMG. Put new Harmonic Balancer back on - no key, so possibly no problems. went on okay, new belt of course. Disconnected a/c so clutch not engage compressor.
    When all hooked up, start car - to an incredible clattering sound. Sounds somewhere between a clanging, scraping, exhaust chuffing and heatsheild rattle all rolled into one.
    OMG
    OMG
    I am halfway to fixing one thing and another descends upon me.
    From research on google the best I can come up with is a dephaser problem. Could it be?
    How so all of a sudden, unless the timing belt has indeed slipped? Possible? unsure, shouldn't have I don't think. Car starts ok, runs a bit rough but sounds dire.
    If timing belt had slipped it wouldn't start so readily I think.
    Getting a bit disillusioned with this car........
    (Copy of my post in your VVT thread):
    Please just read the procedure in my post in your thread on accessory belt breaking (above post #19), and also my thread on steel idler pulleys (link in Jaahns post #18 above) (the steel pulleys doesn't matter, but there are photos and dimensions of the 2 simple tools which can be made cheaply). Also note the HB bolt has to be done up to spec to clamp the crank timing gear (behind the HB) as it does not rely on a keyway - it can rotate if HB bolt is not tight enough. From memory the HB bolt is lightly tightened to 20nm then tightened a further 115 degrees - thats what the white gauge in my photos is showing.

    Really, if you don't understand whats happening here, you should take it to someone who can help you.

    Cheers.
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