Oil leak from Gearbox and found Pilot Bush having failed

Discussion in 'C-Class' started by Mahantesh Angadi, Jan 11, 2017.

  1. Mahantesh Angadi

    Mahantesh Angadi New Member


    During my vehicle B (minor) service, my dealer has reported me the following problem:

    Oil leak from Gearbox and found Pilot Bush having failed has caused oil to travel through Gearbox Wiring Harness which has reached the gearbox control unit.

    To fix the problem the dealer has given me an estimate of GBP 3,000 - 3,500. The dealer mentioned that, there is lot of labor work, which might take up about 14 hours of time. If we are lucky we can recover the gearbox control unit by wiping all the leaked oil from it and drying it up provided if it is still intact.

    Could you please advise, what all the dealer has mentioned is very much true?

    My vehicle is under mercedes service care plan and due which I service my vehicle every year from the dealer. Also, I get my vehicle MOTed from the dealer itself. Because of these, since 4 years my vehicle visits the dealer once every 6 months in July time for MOT & January time for Service. In-spite of this, the dealer never reported any leak. The dealer has reported the leak last week 7th Jan when went for B (minor) service. The dealer also mentioned it to be very serious as the leaked oil reached the gearbox control unit. I got little upset with the dealer not to report any minor leak on any occasion of last service (in Jan-2016) or during the last MOT in Jul-2016.

    Could you please advise, this doesn't come under any service or MOT?
  2. engineer

    engineer Member

    Yes what the dealer is saying is possible. Oil can get up to the TCU via the wire harness. As far as if it is covered under any service warranty or MOT I am not sure. Replacing the wire harness is very expensive.

    Has the car been driving fine?

    Why not just replace the pilot bush (13 pin connector) and dry the TCU so there is no oil.

    Has your car even gone into limp mode?
  3. Mahantesh Angadi

    Mahantesh Angadi New Member

    Hi there,

    Thanks for your reply.

    The service manager at Mercedes dealer was not that helpful. He would have advised me like you that, let us stop the oil leak by replacing the pilot bush (13 pin connector), so that we can stop any more oil flows through the Gearbox Wiring Harness and into the Transmission Control Unit (gearbox control unit).

    The car has been driving fine. Hope it means, it hasn't gone in limp mode.

    Any further advise is most welcome.
  4. Kajtek1

    Kajtek1 Active Member

    Dealers don't do washing, only replacement on modules.
    At least they don't force you to buy new car when you drive in with dirty one ;)
    I know 722.6 transmissions pretty well and it was proved hundreds of time that new ca $10 pilot bushing plus ca $10 spend on cleaners solve even transmission limp mode.
    You are lucky your car does not have any problems yet, so doing pilot bushing and wiping TCM dry might do.
    If not, taking TCM board from the box and giving it good bath with MAF or other good cleaner should be sufficient.
    Mahantesh Angadi likes this.
  5. Mahantesh Angadi

    Mahantesh Angadi New Member

  6. Mahantesh Angadi

    Mahantesh Angadi New Member

    Thank you so much for your input.

    Will take to some mercedes specialist (other than dealer) and try get it sorted as you advised. Will update how it goes.
    engineer likes this.

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