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451 CDi - gearbox playing up

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  • 451 CDi - gearbox playing up

    Hi Guys,

    New to the forum, and I hope you don't mind if I jump straight on in with a problem question.

    I have a 2010 MY 451 CDi. Had it a couple of years, and up until last October it was fine, but since then I've been having issues with the gears. Here's some basic info:

    Car works perfectly well on all types of road on my normal commute (urban/country/A roads). Gears do what they should, in either auto or manual (I have flappy paddles ), up and down, all is good. However, I now have a fairly regular 300 mile weekly commute, which it's not liking.

    First issue was an isolated incidence of the clutch not operating correctly - there was no 'take up', 1st gear just came in as though I'd dumped the clutch. Left it for an hour or so, and all seemed to work fine after that. Nothing much happened for a few weeks or so, then I started having issues on a long run.

    Then, on a long 300 mile journey to Gateshead, halfway through pulling off for a break and the car held in 5th as I was slowing down then slipped into neutral - couldn't get any gears, neutral sign was flashing even though I'd tried selecting gears. Turned car off completely, pulled key out of ignition, left it for a few minutes, restarted and away we went, all good. It did this twice more on this journey, and a couple of times on the way back home. For the most part I was sitting around 65 - 70mph, so not thrashing it.

    Basically, since then, it's been doing this on and off on any motorway journey that I do of more than an hour. Always resets after turning off completely and is driveable, but will do the same fault 2 or 3 times at least on each journey. However, the last part of that journey home is about 40 minutes on A roads, and it may do it once more, but after that settles back to being normal, until the next time I'm on a long run. It obviously only happens when I slow down enough on the motorway to need to drop down a gear, but doesn't do it all the time, it's a bit random.

    There have been a few variations on this theme, a couple of times it's changed down, to 4th, then 3rd, then stuck in 3rd and not released, eventually coming to a juddering halt and stalling. Same thing, switch off and let it reset and all is good again.

    I changed the gearbox oil in November, hoping that would cure it, and it seemed fine for a couple of trips, but soon reverted back to type. I'm now an expert at coasting into services and finding a parking spot without having to stop!

    I don't thrash it on the motorway, sticking to around 65 - 70 at most, but I don't dawdle in and around country roads either, so it's not being molycoddled.

    I've read a few things about lubricating/cleanbing the clutch actuator, but this doesn't seem to be a mechanical problem mostly, more of a software issue perhaps.

    Any ideas or advice over what action I can do myself (reasonably hands-on/mechanically minded, I do my own oil/filter changes etc.) would be most welcome before I bite ht bullet and seek professional help.

    Car has 75,000 miles on it now, but I;ve put 50k of those on in the last 2 years. I have to date used only MB oil and filters when I've done the servicing.

    Thanks in advance.

    Clive
    Last edited by Muppet; 12-01-18, 10:30 PM.

  • #2
    I would start by removing clutch actuator, open it out, pull off rubber gaiter and inspect for ingress of water and dirt.

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    • #3
      If a software issue, why did problem take this long to materialise?

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      • #4
        Originally posted by tolsen View Post
        If a software issue, why did problem take this long to materialise?

        I don't know, maybe I'm clutching at straws, but the way it drops out of 5th gear into neutral with the N flashing in the display without even trying to select a lower gears as I slow down points me in the direction - intermittent fault? Or maybe something's getting hot on a longer run that causes the issue, especially as on any other driving the gearbox works perfectly.

        Anyway, thanks for the advice on the clutch actuator, I'll have a go at that today and report back. I'm doing the drive again on Monday so will find out.

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        • #5
          Mjolinor on Smartz had a problem like yours.

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          • #6
            Hmm, that didn't go so well then.....

            Took the clutch actuator off - no visible problems with it, but not much grease in there. Cleaned it up a bit then sprayed loads of white lithium grease in. Put the actuator back on in exactly the same position that it came off, and now it's banging the clutch in with no take up. Have tried numerous different positions and although initially it feels smooth, within a couple of gear changes it goes in with a bang again. Very difficult to pull away from a standstill without it stalling.

            I suppose I'll have to go to a garage and get it set up on a proper Star machine, although driving it there is going to be 'interesting'.

            Any suggestions?
            Last edited by Muppet; 14-01-18, 12:57 PM.

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            • #7
              Were there signs of ingress of water and dirt?
              Unwise to overdo grease application. May upset the automatic clutch wear compensating mechanism and also contaminate motor brush gear.

              Wear compensating mechanism relies on metal to metal friction to work and may slip if coated heavily in grease.

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              • #8
                Here is Mjolinor’’s thread dealing with similar trouble as yours. The inner workings of clutch actuator are discussed mainly on pages 10 -12.
                http://www.smartz.co.uk/showthread.p...-update/page10
                Last edited by tolsen; 14-01-18, 08:37 PM.

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                • #9
                  Originally posted by tolsen View Post
                  Were there signs of ingress of water and dirt?
                  Unwise to overdo grease application. May upset the automatic clutch wear compensating mechanism and also contaminate motor brush gear.

                  Wear compensating mechanism relies on metal to metal friction to work and may slip if coated heavily in grease.
                  No, no dirt or water ingress at all. The motor is higher than the gear, so I don't think grease will get into it. When you press the throttle, the clutch comes in with a bang, the car jerks forward then the clutch disengages and it revs out - I guess this is protecting itself? Trying to get my how this thing operates, does it push in towards the engine when a gear is selected, and release back out to drive off? If so then it may be sticking now - I guess I'll have to take it apart next weekend again and have another go at it.

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                  • #10
                    My 450 Cdi clutch actuator did that. Released clutch too fast causing car to jump forward and engine to stop. Turned out it was a wiring problem. There are six wires to clutch actuator. Two provide power. The four thinner wires provide the incremental rotary encoder signal. In my case two of the encoder signal wires were chafed causing all my trouble.

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                    • #11
                      Originally posted by tolsen View Post
                      My 450 Cdi clutch actuator did that. Released clutch too fast causing car to jump forward and engine to stop. Turned out it was a wiring problem. There are six wires to clutch actuator. Two provide power. The four thinner wires provide the incremental rotary encoder signal. In my case two of the encoder signal wires were chafed causing all my trouble.

                      That's a good shout, I'll check that when I'm back home at the weekend - had to steal the wife's car this week, she's not too impressed!

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