Clutch woes
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Thread: Clutch woes

  1. #1
    1000+ Posts REN TIN TIN's Avatar
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    Default Clutch woes

    My R12 clutch has started to slip.
    One day it was fine, next day I went to take off and the thing was slipping like buggery.
    The pedal seemed much lighter than usual and while the car did move, a lot of revolutions of the motor were not matched by appropriate forward motion. Gear changes were okay, well, as good as they ever are in a 12.

    I've never known a clutch cable to shrink so I doubt it the adjustment of the cable.
    I'll loosen it off a turn just to make sure (when the rain stops).
    I'm thinking two possible culprits, contaminated clutch plate or thrust bearing failure.

    The clutch hasn't been done on the car since I've had it (about 3 years and 5000 miles) so is unknown but while the clutch plate could be worn out, it shouldn't suddenly start to slip. Should be gradual I would have thought.

    I'll have to get the ol' girl towed to the workshop and let them sort it.
    Just had the driveshaft seals done about a month ago so could do without another fail for a while.

    Cheers
    RTT

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  2. #2
    1000+ Posts renault8&10's Avatar
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    Reality is it could be any number of things. There are similar threads already so maybe there is something about the clutches supplied over the last 5-10 years that thy are not standing up to the job?

    Unfortunately, we seem to be in a “take what we can get” mode with our parts these days rather than having options on known quality clutches (and parts generally).

    Consensus of all the various threads seems to be that good quality pressure and driven plates seem to be the key unless there is an obvious cause like oil leak as you summise. One of the other threads concluded that the driven plate had worn and the lower clamping pressure of the pressure plate couldn’t compensate if I recall correctly.
    KB


  3. #3
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    Hi
    My guess from your description would be a cracked diaphram spring. It causes a dramatic loss of pressure. A new pressure plate required and clutch plate while you are there would be my guess.
    Do not get the flywheel resurfaced unless they know exactly what they are doing.
    Jaahn
    Interesting things diaphram springs. They do not have a linear spring rate, but s shaped and as the plate wears the clamping force can increase ?????

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    I believe that what renault8&10 has identified is the most likely cause. A thrust bearing failure is usually associated with the sudden appearance of a new noise which presents most when the clutch is depressed. It causes problems with disengaging the clutch, usually not clutch slipping. The contamination from an oil leak will be announced by a larger puddle under the car and the clutch cable deciding to shorten is not likely at all unless someone has pulled up the adjustment to disengage it. Wear and stretch would do the opposite and make it start to crunch gears, not slip the clutch..

    The engine and gearbox will need to be separated to inspect and fix the problem.

  5. #5
    COL
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    Quote Originally Posted by jaahn View Post
    Hi
    My guess from your description would be a cracked diaphram spring. It causes a dramatic loss of pressure. A new pressure plate required and clutch plate while you are there would be my guess.
    Do not get the flywheel resurfaced unless they know exactly what they are doing.
    Jaahn
    Interesting things diaphram springs. They do not have a linear spring rate, but s shaped and as the plate wears the clamping force can increase ?????
    Yes I agree with Jaahn something like the diaphram springs have broken for such a sudden failure.

    Anyway you are going to need a complete clutch kit (pressure plate, clutch plate & throw out bearing) and an input shaft seal and a bell housing gasket, otherwise you will be doing it again when the input shaft oil seal leaks.

    Also there is a good chance the flywheel will need refacing and if there is a step in the flywheel make sure they keep it at the right depth.
    Regards Col

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  6. #6
    1000+ Posts renault8&10's Avatar
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    When I had a diaphram spring break on my R8 clutch, it was accompanied by an obvious noise when the clutch was depressed. Would'nt a cracked spring have the same effect potentially?
    KB


  7. #7
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    Just in case.

    Check all the bolts are intact and tight on the diaphragm spring to flywheel connection.

    The darn things will yield and fail over time especially if they have been reused.
    Take off flywheel cover under engine and check, rotate flywheel and check all.

    Hopefully is the case, as can change them without separating engine gearbox

    Always use new HT bolts

  8. #8
    1000+ Posts REN TIN TIN's Avatar
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    Thanks for your replies.
    There is a 'noise' when the clutch pedal is depressed, the car's been making this noise for the time I've owned it.
    Didn't seem to affect the operation of the gearbox or the clutch and as there's no real sound deadening in a 12 one just puts up with noises unless they are obviously major.
    Broken diaphragm spring is a possibility and would explain the sudden onset.
    Thanks Driven, I'll check the bolts as suggested.
    Otherwise, I don't have a workshop so will have to get the clutch done by workshop.
    (I actually have a new clutch plate and a used pressure plate and flywheel in my spares pile, maybe even a new throwout bearing too).

    Cheers
    RTT
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  9. #9
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    Quote Originally Posted by driven View Post
    Just in case.
    Check all the bolts are intact and tight on the diaphragm spring to flywheel connection.
    The darn things will yield and fail over time especially if they have been reused.
    Take off flywheel cover under engine and check, rotate flywheel and check all.
    Hopefully is the case, as can change them without separating engine gearbox
    Always use new HT bolts
    Hi Driven
    In all my time working on cars and some crap ones at that, I have never seen the pressure plate bolts loose. It is possible but I have not seen it. I have seen the odd missing one ??

    Indeed the statement "The darn things will yield and fail over time especially if they have been reused" is an alarmist statement that I would consider has little basis in fact. I believe I always reuse the bolts, after inspection to see if they are in reasonable condition. I have worked in third world countries and seen some work practices that are 'suspect' to say the very least but bolts do not yield and fail unless they have been overtightened or overloaded in some manner.

    Sorry to be an old pedantic git
    when you are offering a suggestion in good faith !
    Jaahn
    PS I will add that with cars and tractors etc any odd thing can happen and sometimes does, due to the 'uncontrolled' nature of the servicing and use
    Last edited by jaahn; 17th October 2018 at 09:54 AM.
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  10. #10
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    I have to say I have redone quite few clutches over the years and I have never seen a broken or loose bolt. I always use the old bolts. Further more they are 7 mm bolts that are next to impossible to get new.
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  11. #11
    1000+ Posts renault8&10's Avatar
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    They should be torqued to the manufacturers specification of course, but who among us does that?
    I know I have done so on the last two occasions, but would not dare suggest I've always done it that way!
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    KB


  12. #12
    1000+ Posts schlitzaugen's Avatar
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    Be careful using a spare flywheel on your engine. It is almost certain it will not be balanced with your rotating assembly and the inevitable vibration is going to have only adverse effects on your engine, not in the least loss of power because your engine won't spin freely to its "natural" power band.

    In theory you could find the balancing point of the old flywheel/clutch assembly and try to machine the spare flywheel to replicate that, but once you take the old flywheel out to measure its balancing point it is a lot cheaper, quicker and easier to just reuse it.

    The mass of the flywheel needs to be kept the same as well.

    I don't remember the bolts being 7mm but if that is true, they can be found at dedicated suppliers and if one wants socket (i.e. Allen) head 7mm they can try Maryland metrics (or something like that) in the US. I got mine from them.
    Last edited by schlitzaugen; 17th October 2018 at 03:27 PM.
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

  13. #13
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    Default Hmm ??

    Quote Originally Posted by schlitzaugen View Post
    Be careful using a spare flywheel on your engine. It is almost certain it will not be balanced with your rotating assembly and the inevitable vibration is going to have only adverse effects on your engine, not in the least loss of power because your engine won't spin freely to its "natural" power band.

    In theory you could find the balancing point of the old flywheel/clutch assembly and try to machine the spare flywheel to replicate that, but once you take the old flywheel out to measure its balancing point it is a lot cheaper, quicker and easier to just reuse it.
    The mass of the flywheel needs to be kept the same as well.
    I don't remember the bolts being 7mm but if that is true, they can be found at dedicated suppliers and if one wants socket (i.e. Allen) head 7mm they can try Maryland metrics (or something like that) in the US. I got mine from them.
    Hi Schlitzaugen
    I am going to be an old pedantic git here again !! Twice in one day
    I do not agree with that statement AT ALL. Whether the balance is good or not so good will not affect the way the engine revs or performs in a primary sense in any way.
    It may affect the smooth running and possibly some small extra stress on some parts but that is all. Balance is overplayed IMHO as far as performance is concerned.

    What about a single cylinder engine. They have been extracting power out of them since, well since they were invented and young hot heads found how exciting they were But you cannot "balance" a single, all you can do is move vibrations to a place where it matters less. So balancing a 4 just ensures the out of balance forces get averaged out for the primary forces anyway. The others get fixed by the mounts !!


    The rotating parts can be 'balanced' to the extent the center of mass is in the center of rotation but with modern parts that is not much of a problem anyway. Back in the old days a 15 KG cast flywheel need a bit of balancing but they are long gone as have the cast pressure plates too. The last one I did was a Traction.

    Some engines, eg V6 GM Holden etc which have an odd layout and/or firing order do use an out of balance flywheel to incorporate it into the crankshaft balance weight, but that is not normal practice.
    Cheers Jaahn
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  14. #14
    1000+ Posts REN TIN TIN's Avatar
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    I don't intend to change the flywheel unless there is some sort of major issue with it so balancing (if it is an issue) won't be needed.
    The usual consumables, clutch, throw-out bearing, and maybe pressure plate.

    The pressure plate bolts probably aren't a problem but they only take an hour to check so it's no biggie.

    Cheers
    RTT
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  15. #15
    1000+ Posts Frans's Avatar
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    Quote Originally Posted by Sunroof View Post
    I have to say I have redone quite few clutches over the years and I have never seen a broken or loose bolt. I always use the old bolts. Further more they are 7 mm bolts that are next to impossible to get new.
    Sunroof, Here in NZ we can buy M7 bolts at Supercheap or Repco. Have a look at their rotating stand with those packets labelled
    "Champion". Here there are plenty and high tensile as well. You will have to cut them to size because they will be too long.

    Regards, Frans
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    Old enough to know better
    Young enough to do it anyway.

  16. #16
    1000+ Posts schlitzaugen's Avatar
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    The R12 engine is a happy high revving one. I don't think you'd be able to rev it as high as it can if it were out of balance.
    ACHTUNG ALLES LOOKENPEEPERS

    Das computermachine is nicht fur gefingerpoken und mittengrabben. Ist easy schnappen der springenwerk, blowenfusen und poppencorken mit spitssparken. Ist nicht fur gewerken bei das dummkopfen. Das rubbernecken sightseeren keepen hands in das pockets-relaxen und watch das blinkenlights.

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