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722.6 Transmission Fluid Leaking

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Jim2, May 15, 2019.

  1. Jim2

    Jim2 Senior Member

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    Your Mercedes:
    2010 Eclass w212 2.1 CDI
    Some months ago ( 5/6) the fluid, filter and electrical socket were all replaced by my local Indy. Since then, no problem, But this morning I had to reverse with a loaded trailer (300-400 Kg) on to the lawn. The box seemed to be revving up a bit more than normal, but I put that down to the rear wheels slipping on the wet grass. I disconnected the trailer, and again as I drove off the grass, another bit of slipping, which seemed to stop when I reached the concrete yard. So I drove into town and back out again....20 Klms, and as I drove back into my driveway..I saw a thin line of transmission fluid on the surface. I looked underneath, and there is a drip / drop of trans fluid, straight down from the under shields at the bell housing. Hard to be more specific at this stage, until the trays are removed. Hopefully, it will only be one of the cooler pipes from the radiator, or some minor easily fixed thing.Or even some other similarly looking fluid, coming from some where else.....:confused: Any idea's anyone? I'm taking it into the workshop this evening to put it on the life and try to see what is the cause. But any suggestions of the possible cause would be more than welcome...and also possible costs...
    Thanks
     
  2. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    could be cooler lines, could be sump, most likely to be coolers though.

    Radiators are at the front, if the leak is at the bell housing, then its not that.
     
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  3. OP
    Jim2

    Jim2 Senior Member

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    Yes alexanderfoti, Its dropping down from the splash tray, directly beneath the bell housing..I will really have to wait until it goes on the lift, to be sure. If it really is an oil cooler pipe, but at the back on the housing, and not at the actual radiator at the front, then maybe it's not too bad. I remember very well in Manual gearboxes, where the flywheel bolted on to the crankshaft, there was a seal in the casing ( crankshaft oil seal, if I remember right ) and they used to leak a lot, back in the day. Is there something similar with the automatics? That would cause them to leak from the TC? But if it's indeed from the bell housing / TC/ Transmission, what would normally be the culprit, and is it a big job?
    Thanks, Jim2.
     
  4. LostKiwi

    LostKiwi Senior Member

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    Yes there is a seal on the gearbox input shaft.
     
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  5. OP
    Jim2

    Jim2 Senior Member

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    Thanks LostKiwi.
    I realize that until it goes on the lift tomorrow, and the tray's come down, it's all a bit of conjecture up to that point. And unless it's something highly visible like the cooler pipes,then the trans may have to come out to really diagnose the source of the leaking fluid. I would doubt very much that it's something like the sump gasket, drain plug etc. and the electrical plug and seal's as they all have been done. Which lead's me to think internals. So is there a particular part ( or parts ) in the 722.6 trans that tends to leak? But as I have no previous experience with Merc's in general, or auto transmissions in particular, I am lost. So to be honest, I'm a bit apprehensive.
    But tomorrow, all will be revealed.
    Regards. Jim2
     
    Last edited: May 15, 2019
  6. M80

    M80 Senior Member

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    Your Mercedes:
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    Belly pans off, good clean and monitor.
    I would say that until you can physically trace the source anything else is guessing.
    Fluid drips can lie on the belly pans until a change in angle causes it to over flow.
    Could it be mucky condensation from the AC?
    Mine turned out to be from the crank case breather and easily solved with some self amalgamating tape at a push on connector.
     
    Last edited: May 15, 2019
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  7. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Yes absolutely, better to just take a look rather than guess.
     
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  8. OP
    Jim2

    Jim2 Senior Member

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    I am absolutely praying that it might be something exactly like your case M80...but I have a gut feeling that it is more.:( Its undeniably red fluid, so unlikely to be mucky oily condensation from the AC ( unfortunately ) So I will expect the worst, and hope for the Best,...:D:D:D
    Thanks for your helpful suggestions, I appreciate it !!!
    Jim2
     
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  9. ajlsl600

    ajlsl600 Senior Member

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    at least if it is red and not dark brown so its not burnt/overheated oil . think if yr lucky its a oil line leak and if yr still seeing oil after 20 miles there is still some in it so unlikely to be catastrophic . cross fingers ,covers off look, see .good luck.
     
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    Jim2

    Jim2 Senior Member

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    Yes, ajlsl600, one good point it was changed less than 10'000 Klms ago, so still very red. Only driving it has done is 3.5 miles max.....and that was done in 3 section's. So first thing in the morning...I will check the trans level while cold ( not ideal I know ) but it will be indicative of the amount still in the box, before I drive it to the workshop...again its 3 miles away, and I want to keep oil in it at all costs. So hopefully, it wont turn out to be catastrophic......fingers crossed ( and everything else too !!!! :):):))
     
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  11. OP
    Jim2

    Jim2 Senior Member

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    So I got it on the lift at the Indy's this afternoon, and the culprit? The electrical connection socket to the Transmission.....a part that was replaced less than 5'000 miles ago...I'm a bit dissapointed with this, but on the other hand, I'm relieved too that it's not something far more complicated and expensive.
    So overall, I'm happier this evening that I was yesterday......:):D:):D
     
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  12. M80

    M80 Senior Member

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    Was there evidence that the 'o' ring was damaged?

    I replaced mine, to complete the ATF service, a month or so ago. In truth it was a bit of a git of a job. The new 'o' rings were hard to get back to their seat, even with some ATF wiped over. And being delicate so as not to force things. So I tried the old and they went back easier. Back to the new and still awkward.
    I can see how damaging the new 'o' ring is possible and now question the intelligence of replacing them if there was no leak before hand.

    Because of this I monitored for a couple of thousand miles, not something everyone would do.
    The trouble is there can be confusing residues for a while after a change. Even cleaned up the stuff seems to keep coming back even w/o a leak.
     
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  13. Oldspanners

    Oldspanners Senior Member

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    Depends on the O rings rather than the connector. If it was initially replaced with an older one (with I think it was red or white I can't remember ones) it would leak sooner.
    Anyway sigh of relief!
     
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  14. OP
    Jim2

    Jim2 Senior Member

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    The existing connector has a slight bit of movement in it, and it's very wet. It's the culprit all right. I did not remove it to see it's condition...I'll leave that to the man who fitted it 5'000 Miles ago...:cool: but I will have a look when he has taken it out.
    The whole issue with these connectors is that if they leak, the fluid can ( and does apparently) travel back up through the harness, and destroy the ECU. So all the thrust is for prevention. That was the reason that I wanted mine changed.....I had the trans oil,filter, TC , cooler and pipes all flushed. Only the connector left to do, so I tried to do it myself. My 1st attempt? Failure. Like you was not able to enter the new plug and seals correctly, and bent a pin. Had to put back in the old parts and take it to the expert. Who did it while the sump was taken down ( the conductor plate had to be replaced because of the bent pin.) but he told me that while it's possible to replace the socket in situ, it's better if it's done as part of a trans fluid and filter change.... so you live and learn. another tip I picked up here on the form is to just replace the old seals on the plug, with brand new ones...much easier to do it seem's. But for now, I will take it back to the workshop where it was originally fitted, and we will see how I get on there. I'm just happy that it's nothing more complicated and expensive.
     
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  15. OP
    Jim2

    Jim2 Senior Member

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    Yes indeed Oldspanners....would have been terrible for me if my MB dream were to come to an ignominious end at this point in time... Will have to wait and see now what the rings are like after the workshop who installed them replaces them. But, MB future now looking brighter again !!! :):):)
     
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  16. Taffy7hfa

    Taffy7hfa Senior Member

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    Your Mercedes:
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    When I replaced the pilot Bush on the ML it dripped atf on the drive for about a week before it eventually stopped.
     
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  17. ajlsl600

    ajlsl600 Senior Member

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    this oil in wiring harness issue .have benz sorted that out ? or is that still an issue i would have thought benz would HAVE to deal with that as the item is surely unfit for purpose. no ? do they get away with it state side?
     
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  18. umblecumbuz

    umblecumbuz Senior Member

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    If the mechanic who replaced the pilot bush was not familiar with this gearbox, he might have tried to draw the bush into its housing by tightening the captive setscrew in its centre. WRONG!
    The setscrew is intended to hold the bush in its housing once it has gone 'home' - not to pull it in.
    The O rings need to be 'worked' into position first, then the setscrew is just nipped up to hold the assembly together - preferably while the bush is being pushed inwards.
    The setscrew goes into a small brass bush moulded into the conductor plate. This bush can easily work free if abused, and that will give all sorts of headaches when the time comes to work on the gearbox internals.
     
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  19. OP
    Jim2

    Jim2 Senior Member

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    That's really strange.....I can understand some fluid leaking out during the fitting, but afterward's???? I mean after extracting to old socket, aside from some light fluid coating on the new one, any excess fluid would have been cleaned off. I never had that with mine. Until 9'000 Klms later when I tried to reverse the trailer onto the grass surface ( it was wet from the dew, and the trailer was loaded ) the wheels were spinning, and the engine revving, I think that what happened was that the fluid was really " stirred up" to the extent that some of it was forced out through the connector plug seal's. This is my theory anyway, but I don't have any other explanation for it. It has not happened since that one time.
     
  20. Oldspanners

    Oldspanners Senior Member

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    That's because the oil had wicked its way up the wiring harness the same as happens with cam magnets on the M271 and it was draining back out of the harness and not the gearbox.
     
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