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  1. #1
    Super Member California's Avatar
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    Default Yanmar YM186D Power Steering hydraulic dribble

    I finally bought a YM186D with power steering and a loader. It needs some minor tinkering to put it in service.

    There is a tiny round bleed hole on top of the power steering hydraulic cylinder unit. This hole is at the front end of the tiny secondary cylinder that controls and sends fluid to the steering cylinder when the steering wheel is turned. It squirts if I turn and haven't turned for a while. My first guess is it should be an air vent and this is hydraulic fluid that got past the control cylinder's piston ring.

    Has anyone seen, and fixed, this issue?


    Also - this has a Yanmar YFL 650 quick-detach loader. About the same thing as a modern Koyker. All four quick-disconnects, and all the hoses, are covered with oil. I can't tell yet if I see years of never-cleaned oil on the hoses or actual dribbles. Anyone fixed that, too? I expect I will have to get four new hoses made.

    Edited - better description that the vent on the little control cylinder leaks; it's not the main steering hydraulic cylinder that leaks.
    Last edited by California; 11-06-2013 at 08:50 PM.

  2. #2
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    Where are the pictures? May not help you but the 3rd and 6th posts in this thread show the manual for the 186 power steering. http://www.tractorbynet.com/forums/y...-assisted.html

  3. #3
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    Congratulations on the new machine! I hope it serves you well.

    On my tractors with quick connects, I have yet to experience one that doesn't dribble a cc or two when it is connected or disconnected. That may just be because everything I have is old, or they may all be that way. Even new ones have done it for me, though. It may simply be an accumulation of attaching and detaching the lines over time. Loader lines seem especially prone to being damaged and leaking though, with the sharp kinks, repeated motion, and lots of sun exposure. It may be a combination of things as well.

    To echo the rest, share pictures. I'm excited for you!

  4. #4
    Super Member California's Avatar
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    Quote Originally Posted by winston1 View Post
    3rd and 6th posts in this thread show the manual for the 186 power steering. http://www.tractorbynet.com/forums/y...-assisted.html
    Thanks!!! I'll go look at that.

    This afternoon I pressure-washed the whole rig. Obviously this former landscaper's tractor hasn't been taken to the carwash for years; portions of several decals were curled and this blew them right off. Now it looks like a couple of disconnects may be the source of the loader hose mess rather than all of them. And I put on a temporary diaper to deflect that occasional spurt from the steering unit, until I can get it fixed. These leaks surprise me - my first YM186D (no loader) has no leaks at all. Looks like disconnects are simply an unavoidable source of trouble - at least on 30 year old equipment.

    I'll start a thread separate from this repair thread, with pictures of the new toy.
    Last edited by California; 11-06-2013 at 09:15 PM.

  5. #5
    Super Member California's Avatar
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    Winston Thanks!!! I never expected to see the complete Steering Kit install manual. That is very helpful!

    I've edited this post to be complete in case someone can learn from it for their own project. I strongly recommend download all the Manual pages, 3 through 16, that Winston linked to above.

    Scan 9 in the thread you referenced shows the little secondary hydraulic control cylinder I'm talking about. Its on top of the main hydraulic cylinder and much shorter. The bleed hole that occasionally spurts is near the front end of that little cylinder. The drag link from the steering box Pitman arm pushes/pulls the piston in that control cylinder.

    And Scan 3, Manual page 11 shows the control piston where I think the o-ring at the end of the piston is leaking. That should be easy to replace. Well, after taking the valve apart and removing Pin #4 which blocks removal. I see that the o-rings are the only user-maintainable parts on that piston rod; the rest of it is factory-calibrated. Note the re-assembly instructions on Manual page 12 (Scan 4) require that all accessible o-rings should be replaced after opening this actuator assembly.

    Edit, added - and ... following your link, here is mnoonan's photo of the YM186 power steering assembly. It shows the little control cylinder on top of the main cylinder. (Wish mine were that clean!) Source - his 2011 thread Yanmar YM186 power steering question.

    Last edited by California; 11-07-2013 at 12:49 PM. Reason: I'm still learning from studying that Manual ... Thanks Winston!

  6. #6
    Super Member California's Avatar
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    I solved the loader's leaky quick-disconnects problem - for under $1.

    It didn't need four new hydraulic disconnects ($65+) or new hose assemblies made up ($$$), which was my first impression with so much oil everywhere.

    When I cleaned up the mess and looked for the cause, I found that the disconnects labelled Parker-Pioneer (Parker 4050-3, ISO 5675) seal at an o-ring, just beyond the lock balls, that just takes a moment to replace. My $4 HF o-ring kit contained the correct (SAE) rings. Problem solved.

    -ag-set-2t-jpg

  7. #7
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    After you remove the flat cover, remove the actuator parts inside. Then you will be able to unscrew the actuator and pull it out. On it you will see the o-ring that needs to be replaced. It's really pretty simple.

  8. #8
    Super Member California's Avatar
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    Default Re: Yanmar YM186D Power Steering hydraulic dribble

    Gjamtrac, thanks for the encouragement. After looking at the manual that Winston posted I wasn't clear if this would be simple, or one of those tasks where I would need to find a power steering specialist to reassemble the darn thing.

    The manual cautions against taking apart the calibrated centering component. (on that rod with the o-rings). Also behind the disc in the main casting there seems to be a preloaded spring that they caution 'needs specialized equipment' if it is removed. It sounds like replacing the o-rings doesn't disturb either component.

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