Megane death rattle - or VVT dephaser. Oh My Gosh
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Thread: Megane death rattle - or VVT dephaser. Oh My Gosh

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    Tadpole
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    Default Megane death rattle - or VVT dephaser. Oh My Gosh

    Hi,
    Anyone got any thoughts on where to start with frightening rattle in Megane 2 litre engine?
    From google searches it seems it could be to do with the VVT. There is a VVT dephaser - never heard of such a thing before, and a dephaser pulley to boot.
    Never heard about these things before but from the stuff on google they do fail.....
    Whichever way you look at it, it looks tricky and expensive.
    Anybody have any experience with these things? Do you check the solenoid first? Is it easy? and how do you determine if it is failing and then the pulley - big job there by the look of it and special tools needed.
    Oh dear.
    Was hoping I had just knocked the lead off the solenoid accidentally, but alas it is all hooked up.
    help....

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    1000+ Posts Fordman's Avatar
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    Bluemegane,
    You really should have put in this post that you have just replaced the harmonic balancer - and it looks like you did it without the tools to lock the cam timing.
    So in my opinion, the clattering etc noise when started is MOST LIKELY (not 100% - nothing ever is) because the cam timing has slipped.
    I would forget the VVT red herring until you have checked the cam timing - it may be too late but cross fingers.

    Please just read the procedure in my post in your thread on accessory belt breaking, and also my thread on steel idler pulleys (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.

    Good luck
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    Hi Bluemegane :0
    It has all been said by the other posters. I will just add for your information and others who may read this after, that most newer engines must not be worked on without knowing what can go wrong. Anything to do with the front pulleys and the timing belt must not be done until you know what the procedure is. Even if you do not understand what is the purpose of the procedure. The engine can be written off if you do it wrong. A "simple" change of timing belt can be very expensive done wrongly. This applies to all makes.

    I hope you get away without having bent all the valves !!
    Good luck Jaahn

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    Thanks for the feedback. But I am still not clear about the relationship between the accessory belt and the timing belt. As far as I can determine they are not synchronised in any way other than sharing the drive from the crank. Yes the harmonic balancer outer pulley separated from the centre spindle but it did not come adrift from the shaft. I had to remove it using full tension, and the timing cog behind it had no opportunity to move as it is located on a key as has been noted.
    Provided the belt cog was not disturbed and I bolted on the new harmonic balancer to the correct tension, I don't see how the valve timing could have altered.
    I was not driving the car at the time the accessory belt broke and from what I can glean about the incident, I get the idea the accessory belt broke and the car was then driven until the battery gave up. Which further confirms the accessory belt operates completely independently to the timing belt.
    I am not completely without knowledge about engine timing as I have replaced timing belts on two Hondas, two Mitsubishis and a Hyundai diesel earlier this year. I have also rebuilt a Renault 12 engine - but that of course did not have a timing belt. I do know how they work. I am however new to VVT and am asking around to see if there is anything for the unwary to know about these systems.
    As for taking the car to someone who knows.... I fear that was the beginning of my problem. I took it in to have the a/c regassed professionally and I think they did not do it correctly thus causing problems with the compressor that caused the belt to snap twice.
    I don't know of any Renault specialists near me but if I did I would certainly be making tracks to their door. Lol.

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    Quote Originally Posted by Bluemegane View Post
    Thanks for the feedback. But I am still not clear about the relationship between the accessory belt and the timing belt. As far as I can determine they are not synchronised in any way other than sharing the drive from the crank. Yes the harmonic balancer outer pulley separated from the centre spindle but it did not come adrift from the shaft. I had to remove it using full tension, and the timing cog behind it had no opportunity to move as it is located on a key as has been noted.
    Firstly, I think you were on the right track when you concluded the accessory belt snapped because the A/C compressor locked up. I followed that diagnosis with interest, because I have not experienced it before, but it makes sense that it was the cause.

    And, yes, in operation there is no synchronisation between the timing belt and the accessory belt. It merely uses the HB pulley as the driver.

    BUT, no, if you reread our comments, the point is there is usually NO KEY on the crankshaft sprocket driving the camshaft timing belt. The sprocket is located only by the clamping effect of the HB bolt. When the bolt is loosened, the sprocket "may" turn on the crankshaft, changing the cam timing. This could occur because of the valve springs "centralising" when the belt was released.

    Not saying this is definitely what has happened, but it seems most likely.

    OK, I believe you can check the valve timing without removing the timing cover, this would be my next step on your engine.
    You will need a piece of 8mm round bright steel rod about 150mm long, or even a 8mm bolt at least 100mm long will suffice.
    The only parts you will need are the 2 plugs which cover the back end of the camshafts, they are like rubberised core plugs, and probably only available genuine, unless you can remove them undamaged. Be careful not to damage end of camshafts when removing plugs from head. See photo with cam tool installed for reference. At this stage, to just "check" the timing, that tool isnt required.

    I would remove the cam cover plugs from back of head.
    Then remove number cyl#1 sparkplug, so TDC can be roughly located using a screwdriver on the piston. In fact remove all sparkplugs to make turning the engine easier. There are no TDC marks on the HB for obvious reasons.
    Turn the engine clockwise by hand with a socket on the HB bolt, until you get TDC on #1 cyl as close as possible.
    At this point you should be able to insert the 8mm rod into the side of the block, to locate the exact TDC as the pin will find a slot in the crankshaft - may take a couple of degrees movement each way of the crank to get the pin to drop into the slot. (The hole for the pin is behind a Torx bolt just behind the bottom of the dipstick tube.
    Now look at the back of the camshafts - if the slots in the camshafts are EXACTLY HORIZONTAL then the cam timing is good. A tool made up from 5.0mm machined flat bar, shaped similar to what is shown in my photo, should be able to be inserted in the slots, but probably a visual check will suffice at first, if you get the drift.

    Megane death rattle - or VVT dephaser. Oh My Gosh-p1100728_red.jpgMegane death rattle - or VVT dephaser. Oh My Gosh-p1100730_red.jpg

    I have suggested this in good faith as a possible way just to diagnose whether your timing has slipped or not. If it is not perfectly aligned still, then valve damage "may" have occurred, also the next step to correct the problem would be another procedure. This is what I would be doing to check it out without spending too much.

    Good luck.
    Cheers.
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    Good tips Fordman.

    In my very younger days I helped a mate replace a cam belt on a Fiat twin cam. We did everything as it should have been done - except tighten the tensioner. A manual turn of the engine didn't show any problem because there wasn't enough inertia to move the tensioner. As soon as the key was turned the cams pulled the tensioner fully slack and that was enough to change the timing enough so that 4 valves were bent. What amazed me was how undramatic it all was - except for the fact that the engine wouldn't start.

    Some engines certainly don't need much misalignment of the timing for things to go badly wrong. The check of the timing on the end of the cams would have to show it to be very very close to correct to not worry about anything.

    Next step a compression test ?

    Cheers

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    Quote Originally Posted by N5GTi6 View Post
    Good tips Fordman.

    In my very younger days I helped a mate replace a cam belt on a Fiat twin cam. We did everything as it should have been done - except tighten the tensioner. A manual turn of the engine didn't show any problem because there wasn't enough inertia to move the tensioner. As soon as the key was turned the cams pulled the tensioner fully slack and that was enough to change the timing enough so that 4 valves were bent. What amazed me was how undramatic it all was - except for the fact that the engine wouldn't start.

    Some engines certainly don't need much misalignment of the timing for things to go badly wrong. The check of the timing on the end of the cams would have to show it to be very very close to correct to not worry about anything.

    Next step a compression test ?

    Cheers

    Justin
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    As Fordman has said, there is usually no key on the crankshaft sprocket.
    I will tell you there is NEVER ANY KEY there.
    Sure, the crank may have a key slot machined into it, but don't go looking, it aint there.
    You may assume and hope that you were so careful removing the crank bolt, but I can
    assure you, it will have turned as there is a lot of tension on it.
    Forget about the "dephaser problem" for now, and follow the procedure of removing the
    camshaft plugs, and slowly turning the engine by hand to get both of the slots in the end
    of the cams to line up. At this point, you should be able to slide a suitable long pin punch,
    the shank of a drill, or similar into the locking slot of the crank. No success? then turn the
    crank one more turn, the cam slots will line up again ( having turned 180 deg.) and you
    should now be able to engage the crank slot.
    If both of these attempts fail, YOUR CRANK SPROCKET HAS TURNED!!
    If one attempt succeeds, go buy a Tatts ticket.
    In this case, if you are 100% CERTAIN that your cambelt timing is correct, start the engine,
    and with your eyes and ears over the engine, slowly raise the revs and observe if the
    death rattle disappears. This would indicate a dephaser or control fault.

    All the above free advice is purely to assist you to get yourself out of the poo.
    i absolutely take no responsibility for any consequential loss -

    BECAUSE FREE ADVICE IS WORTHLESS!!

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    Ah finally I have heard you. I had assumed the timing belt lower toothed pulley was keyed to the crank as is the case on everything I have ever seen. I was unaware that this is not so on the megane engine. So indeed my timing may be way out. In which case I'm in strife!
    I guess I am going to have to autopsy the damage now.
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    Quote Originally Posted by Bluemegane View Post
    Ah finally I have heard you. I had assumed the timing belt lower toothed pulley was keyed to the crank as is the case on everything I have ever seen. I was unaware that this is not so on the megane engine. So indeed my timing may be way out. In which case I'm in strife!
    I guess I am going to have to autopsy the damage now.
    Hi Bluemegan
    Sorry that you have to learn this way. But there was advice given before.
    To comment on this statement "I had assumed the timing belt lower toothed pulley was keyed to the crank as is the case on everything I have ever seen"
    Your previous experience is no longer valid, and not just for a Megan engine but most European engines of both petrol and diesel. For technical reasons they do this or have wide keyways etc. No keys on the cam wheels I discovered on a VW diesel Golf years ago. After the guy had done a "simple" timing belt change. That engine was a writeoff.
    Now we all must assume we do not know how to do it until we have seen the factory recommendations for the job.
    Jaahn

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    Quote Originally Posted by jaahn View Post
    Hi Bluemegan
    Sorry that you have to learn this way. But there was advice given before.
    To comment on this statement "I had assumed the timing belt lower toothed pulley was keyed to the crank as is the case on everything I have ever seen"
    Your previous experience is no longer valid, and not just for a Megan engine but most European engines of both petrol and diesel. For technical reasons they do this or have wide keyways etc. No keys on the cam wheels I discovered on a VW diesel Golf years ago. After the guy had done a "simple" timing belt change. That engine was a writeoff.
    Now we all must assume we do not know how to do it until we have seen the factory recommendations for the job.
    Jaahn
    A practical demonstration of three things, perhaps:

    1) Modern technology is not always better engineered that the "superseded" counterpart.

    2) Cheap at shit engineering implementations can still work as well as those employing "good engineering practice"

    3) Manufacturers focus on speedy production rather than ease of service.

    And I'd suggest it's not the only Europeans or vehicle manufacturers who have realized this. It is evident in nearly any modern product.
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    Hi
    For the benefit of everyone. It is always recommended after any work that might impact the valve timing, to remove the plugs, and turn the engine BY HAND. That means no big handles on the sockets or long spanners. The engine should turn freely with small effort to compress the valve springs the only resistance. Anything more is interference and must be looked at without forceing it. Two full turns is the minimum but more does not hurt.

    I always do that check now no matter how confident I feel. Even though new engines make removing the spark plugs a pain !!
    jaahn
    Last edited by jaahn; 25th February 2018 at 03:43 PM.

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    Quote Originally Posted by jaahn View Post
    Hi
    For the benefit of everyone. It is always recommended after any work that might impact the valve timing, to remove the plugs, and turn the engine BY HAND. That means no big handles on the sockets or long spanners. The engine should turn freely with small effort to compress the valve springs the only resistance. Anything more is interference and must be looked at without forceing it. Two full turns is the minimum but more does not hurt.

    I always do that check now no matter how confident I feel. Even though new engines make removing the spark plugs a pain !!
    jaahn
    Read my post a couple of posts earlier - if only this was a guaranteed test 100% of the time !

    Cheers

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    Quote Originally Posted by robmac View Post
    A practical demonstration of three things, perhaps:

    1) Modern technology is not always better engineered that the "superseded" counterpart.

    2) Cheap at shit engineering implementations can still work as well as those employing "good engineering practice"

    3) Manufacturers focus on speedy production rather than ease of service.

    And I'd suggest it's not the only Europeans or vehicle manufacturers who have realized this. It is evident in nearly any modern product.
    I see it in a completely different light and would say it is a practical demonstration of only one thing....

    "If you don't follow the accepted method, You'll royally bugger it up."

    From
    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
    to
    I had assumed the timing belt lower toothed pulley was keyed to the crank as is the case on everything I have ever seen. I was unaware that this is not so on the megane engine
    demonstrates this with sparkling clarity.

    Renaults are not especially hard to work on, but like boiling a soft boiled egg, easy to get right and easy to get wrong.

    And I suspect the old Aussie myth of "bloody Renaults, nothing but trouble" will now have a bit more milage up north!!!

    Jo

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    Clamping a critical drive component to highly loaded shaft as a sole method of fixing ain't exactly "good engineering practice"

    But I'm probably too old to be smart enough to pass legitimate comment.

    Studying documentation don't change poor design.

    And for the cost of key the bean counters could have let the the job be done properly.
    Last edited by robmac; 25th February 2018 at 06:53 PM.
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    Bean counters never let the job be done properly, they always know better, hence the issues.

    On the other side it keeps us in a job too, fixing their f'ups. Design like this heightens the chance you spend your hard earned money with them.

    My fist engine ever the gti6, turned it over many times to make sure.
    Last edited by Matthew; 25th February 2018 at 07:06 PM.
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    Default The real reson for lack of keys !!

    Quote Originally Posted by robmac View Post
    Clamping a critical drive component to highly loaded shaft as a sole method of fixing ain't exactly "good engineering practice"
    But I'm probably too old to be smart enough to pass legitimate comment.
    Studying documentation don't change poor design.
    And for the cost of key the bean counters could have let the the job be done properly.
    Hi Rob et al
    Actually I believe that the cost of a key is not material to the lack thereof. It is actually to do with the minimisation of pollution and fuel economy.

    Because the most important things in a IC engine occure at TDC and valve overlap has such an important effect on pollution at idle and low speeds they have attempted to minimise production variability by a new method. There are significent tolerances that affect the production of engines and the assembly. So having a flexible way of ensuring the timing of the cams can be set exactly to the crankshaft TDC enables a better outcome all round. That is why they all do it now.

    Perhaps the bean counters determined that this was cheaper than holding all the parts to a much higher tolerance but we will not pay more for better quality and cars get cheaper all the time. And why does it matter because most cars never have the engine opened up for work anyway.
    Cheers Jaahn
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    And why does it matter because most cars never have the engine opened up for work anyway.

    I guess it depends if define regularly replacing a cam belt as "work" or "opening" the engine.
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    Quote Originally Posted by robmac View Post
    Clamping a critical drive component to highly loaded shaft as a sole method of fixing ain't exactly "good engineering practice"
    How many Renault engines have lunched themselves with piston/valve interference (timing belt change failures don't count)????

    I have not heard of any.

    Jo

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    I have not heard of any.
    Nor have I.

    Regardless, a key and key way beats a clamp for reliability and accurate indexing every time.

    As several decades of mechanical engineering practice has proven.
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    I think I have mastered the concept of single and double overhead cams, and had an understanding of the Triumph Dolomite Sprint valve system, but I still have yet to work out how variable valve timing works, so I will leave it to professionals to work on our vehicle!
    It's another lovely day! Again!

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    There is nothing magical about the camshaft arrangement in these vehicles, all you need to do is get the relevant information and tools to do the job. The rest is just a matter of following the procedure set out in the relevant information you have acquired.

    I did the timing belt in my 2002 Renault Laguna V6, I have never changed a timing belt before, but managed to do the job after doing some research and acquiring the right info and tools.
    Regards Col

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    Quote Originally Posted by jaahn View Post
    Hi Rob et al
    Actually I believe that the cost of a key is not material to the lack thereof. It is actually to do with the minimisation of pollution and fuel economy.

    Because the most important things in a IC engine occure at TDC and valve overlap has such an important effect on pollution at idle and low speeds they have attempted to minimise production variability by a new method. There are significent tolerances that affect the production of engines and the assembly. So having a flexible way of ensuring the timing of the cams can be set exactly to the crankshaft TDC enables a better outcome all round. That is why they all do it now.

    Perhaps the bean counters determined that this was cheaper than holding all the parts to a much higher tolerance but we will not pay more for better quality and cars get cheaper all the time. And why does it matter because most cars never have the engine opened up for work anyway.
    Cheers Jaahn
    In regard to the keyless pulleys, I agree with Jaahn, this is not about saving money, but improving the method of accurately setting valve timing. Anyone who has gone the extra mile in getting the valve timing accurate (generally for maximum performance) will use some sort of vernier adjustment in one of the timing gears/pulleys, spending maybe several hours measuring and adjusting valve timing, something not usually worried about with mass-produced engines, near enough was good enough. But now with critical laboratory measurements needing to be replicated in the mass production, this system that Renault have adopted is quite clever engineering, enabling dead accurate valve timing at the assembly with virtually no set-up time, and no special components. And at belt replacement, it is just as easy for the repairer, and the tools required are both simple, and able to be hand-made easily.

    This doesn't change my attitude to the plastic idler pulleys - that (IMO) is a cheapskate design, for saving money and materials. I believe the plastic idlers have made them the critical item for failures, resulting in a low estimated life. Expensive replacement every 4 years is just ridiculous, when a car covers low kilometers like ours. A job made quite difficult (again IMO) by the lack of foresight in engineering in some simple design changes to improve in-situ accessability.

    Back on the keyless pulleys, one just needs to get one's head around the benefit of the design, and accept that the clamping effect of correctly torqued bolts is a reliable method of assembly.

    It will be interesting to hear how Bluemegane's engine pans out - and whether our "assumption" of allowing the timing to move, is in fact the problem.

    Cheers
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    Fascinating thread for which many thanks and good luck with that engine. By chance we caught our Scenic as the compressor started seizing! Agree 100% re the plastic idler wheels as they seem a common failure �� Cheers
    JohnW

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    Quote Originally Posted by Fordman View Post
    In regard to the keyless pulleys, I agree with Jaahn, this is not about saving money, but improving the method of accurately setting valve timing. Anyone who has gone the extra mile in getting the valve timing accurate (generally for maximum performance) will use some sort of vernier adjustment in one of the timing gears/pulleys, spending maybe several hours measuring and adjusting valve timing, something not usually worried about with mass-produced engines, near enough was good enough. But now with critical laboratory measurements needing to be replicated in the mass production, this system that Renault have adopted is quite clever engineering, enabling dead accurate valve timing at the assembly with virtually no set-up time, and no special components. And at belt replacement, it is just as easy for the repairer, and the tools required are both simple, and able to be hand-made easily.

    This doesn't change my attitude to the plastic idler pulleys - that (IMO) is a cheapskate design, for saving money and materials. I believe the plastic idlers have made them the critical item for failures, resulting in a low estimated life. Expensive replacement every 4 years is just ridiculous, when a car covers low kilometers like ours. A job made quite difficult (again IMO) by the lack of foresight in engineering in some simple design changes to improve in-situ accessability.

    Back on the keyless pulleys, one just needs to get one's head around the benefit of the design, and accept that the clamping effect of correctly torqued bolts is a reliable method of assembly.

    It will be interesting to hear how Bluemegane's engine pans out - and whether our "assumption" of allowing the timing to move, is in fact the problem.

    Cheers
    In regard to the keyless pulleys, I agree with Jaahn, this is not about saving money, but improving the method of accurately setting valve timing.
    I hear what you say about valve timing.

    However in a mass production scenario, I am at a bit of a loss to understand how major differences between engines could occur. And mass production in the past and many current engines has not seen adjustable pulleys or sprockets employed.

    I can understand why vernier adjustment is required, with milled heads and custom cams and other modifications.

    But I fail to see see any benefit in a mass production engine, especially with the excellent tolerances to which engine manufacturers work to.
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