AAaaarghh, possible gearbox failure

Discussion in 'Motorhome Chat' started by DavidG58, Aug 5, 2015.

  1. DavidG58

    DavidG58 Funster

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    I do have a habit of panicking without cause on many occasions, but every now and again I am right

    This time I fear the worst

    For a while now we have had odd issues with the engine management on our Mercedes MH going into 'limp' mode, or so I thought at least, massively reduced power for no obvious reasons, even with Bev driving, so not just me :)

    Pull over stop engine, key out and in again all OK, often for 100's of miles, today had to stop 6 times in 80 miles, the last time, close to home at least, 2 times coming up hill to our house it didn't reset, so limp mode up hill = 15mph, = Mr Unpopular by the top of the hill

    My real concern is that immediately after one of the stop to reset incidents we had an awful metallic crunch from somewhere under my feet, but reassured by then driving 40 odd miles with no issues or noises

    I am now home and booked into workshop tomorrow, but not sure if we will make the 10 mile journey, in some ways the worst case scenario is no obvious fault in morning, nothing on diagnostics (typical for me when taking a fault to a garage) then we set off for Bristol on Friday and partially block the M1 in rush hour :(
     
  2. kip

    kip Funster

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    You say you've had issues for a while now, just wondering why you didn't take it in sooner? Fingers crossed it's something that can be fixed easily & cheaply.
     
  3. DavidG58

    DavidG58 Funster

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    it has been in for various checks, nothing shows up on diagnostics

    had gearbox oil changed as a precaution 3 months ago, MH has only done 20K miles over 5 years

    I hope something shows up tomorrow, but hope it is not too expensive
     
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  4. kip

    kip Funster

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    Oh I see, best of luck. (y)
     
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  5. Ethle the wondervan

    Ethle the wondervan

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    Sounds like serious lack of use.
     
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  6. DavidG58

    DavidG58 Funster

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    we have done 18K in the last 2 years though, since we bought it :)(y)
     
  7. Ethle the wondervan

    Ethle the wondervan

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    You've frightened it!
     
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  8. RS_rob

    RS_rob Funster

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    Limp Mode eh!
    what engine you got ?
    Possible overboost by the turbo engaging limp mode same a VW ? if so cured by winding back the nut on the wastegate due to these engines being very sensatively set.
     
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  9. dave newell lvs

    dave newell lvs Trader-Vehicle Services

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    "My real concern is that immediately after one of the stop to reset incidents we had an awful metallic crunch from somewhere under my feet, but reassured by then driving 40 odd miles with no issues or noises"

    So you heard "an awful metallic crunching noise" but instead of getting it checked you drove a further 40 miles? Personally I'd have pulled over and got out to see what made that "awful metallic crunching noise" just in case it was a mechanical failure in suspension or brakes.

    D.
     
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  10. Chris

    Chris Funster Life Member

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    Hope the workshop sorts it out for you(y)
     
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  11. funflair

    funflair Funster Life Member

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    Hi David

    As you say, hope they find something as it's been going on a long time now, I can't imagine there would be much problem with the gearbox that would put it into limp mode. Quite possibly turbo over boost as suggested as I believe hills have featured in the run up to the limp issue on several occasions.

    Fingers crossed.

    Martin
     
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  12. DavidG58

    DavidG58 Funster

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    My knowledge of mechanics is limited to looking and trusting I notice anything changing, in the same way I normally know I have a puncture without actually looking at the wheel

    I had noticed a massive lack of power, I am fairly sure I would have felt a change in suspension or felt a difference in braking, I did opt not to join the motorway and drove steadily along a straight road to a layby. Nothing obviously wrong, so yes I did continue, we all have different skills in life, thankfully in my case I can earn enough to pay to put right my mechanical failings (y)(y) and help keep workshops gainfully employed :)
     
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  13. busby

    busby Funster

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    Whats a limp mode,,,,mine doesn't even have a cat or so i am told...Hope its not serious,,,BUSBY:):)
     
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  14. Terry

    Terry Funster

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    Hi David I dont think the gearbox will be at fault (you have automatic) it will be it's brain that's frazzled:( Are you into the Merc dealers ?---If so ask them to get a 16 year old to fix it :LOL:Seriously hope they find something (y)and hope it's not too expensive
    terry
    edit just been reading on faults on cars and mercs are prone to PCB probs with dry solder joints -this can be fixed a lot of the time by remelting the bits of solder with a very hot air gun thing.No idea if that's what is up with yours or if your garage would know/undertake such a thing but may be worth going to a specialist if they cannot diagnose any faults
     
    Last edited: Aug 6, 2015
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  15. etap

    etap

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    Davidg58,
    Look up Mercedes Medic.com enter limp mode it might cheer you up.
    Etap
     
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  16. DavidG58

    DavidG58 Funster

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    Limp mode I think is some kind of too clever for its own good in most cases electronic restriction on the power output, so in theory if something has 'sort of' failed but it is still safe to continue but slowly, the engine management takes over

    In most cases I think it is over cautious, but I am no expert :)
     
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  17. DavidG58

    DavidG58 Funster

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  18. StefAndDi

    StefAndDi

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    @DavidG58

    I think I'm right in saying that you have the same, or similar, engine and gearbox as me.
    This reminds me of something which I experienced shortly after I purchased the vehicle, although I did not have the metallic crunching noise.
    I noticed that on one trip I was struggling to pass some vehicles. When I pulled over and checked the settings on the steering wheel buttons I found that somehow I had managed to select 'winter tyres' mode and the computer was restricting me to, I think, 50 mph.
    I'm not saying for one moment that it's the same issue. I just thought it might be useful to throw it into the mix because at the time it was a little concerning.
    I hope you get things sorted out quickly and without too much expense.
    Stef.
     
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  19. DanielFord

    DanielFord Funster

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    I'm not sure gearbox failure would cause limp mode. Metallic crunch, quite possibly.
    Either way, I feel your pain, ours is booked in to have the synchro rings replaced on 3rd, and possibly 2nd gear. On the plus side, I am in hospital so will be unable to drive for about a month, so ups and downs all around!
    I don't think our gearbox issues were helped too much when a crazy Itallian swung in front of us yesterday and then pulled an emergency brake to make his exit. I accidently grabbed 3rd instead of 5th at 60mph! D'Oh!
     
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  20. GWAYGWAY

    GWAYGWAY Funster

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    Depending on engine gearbox pairing, probable cause is the gearbox fluid level if it is an auto box. you need to get the right dipstick level and use the right auto fluid, merc's own, If there is a low level the gearbox will be clunky and probably suck in second gear, to stop you wrecking everything the ECU will restrict the engine output to limp mode and 30mph to stop the gearbox being damaged.
    If there is no dipstick you will need to buy one,and dip the fluid yourself. DO NOT OVERFILL or underfill as either will cause the seal and pump to leak or not work. The box has a valve chamber of many sliding valves to direct the fluid to the correct brake in the box that allow the brakes to release one brake and then stop another as it changes up then. As they are seven gears it is a busy box and does depend on the fluid for lubrication, actuation and COOLING, Standing around can allow the oil to drop gunge in the valve chest.
    It might be wisest to run it and then change the fluid altogether if there are suspicions about it's state.
    The ECU will not necessarily record the fault as it is released on stop and start but it may be in a memory if you can have a good reader on it.
    ! Check the gearbox fluid.
    2. Top up if low to the full mark
    3. check the fluid again after topping up as it will have been spread about the gearbox.
    hope that this might help.
     
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