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  1. #1
    New Member
    Join Date
    Feb 2010

    Default Bobcat skidsteer 643

    Hi all
    This is my first try with
    I am English living in Spain and I bought a old Bobcat 643.
    Out here there is no help, very few dealers and no handbooks or workshop manuals to look at....
    My machine leaks hyd oil into the engine compartment when stood or running ?
    I have checked ever pipe / valve I can find and they all seem dry, I was hoping to find a wet one and follow to a leak but no....the area under the cab seems dry and I have checked the chain case level to see if it's leaking in there and out the breather but again on level.
    As there's not much room to get your head in there to look about's a guessing game...I wondered if there is a seal where the engine connects to the hyd motor ! but looking thought the viewing hole in the air cooling/plastic cowl it seems fairly dry in there to ??.
    The oil seems to leak when engine stopped and just stood on level ground ??

    Any one out there have any ideas they would be good enough to share
    with me ?????
    I would hate to strip loads of it down to find out I'm barking up the wrong tree


  2. #2
    New Member
    Join Date
    Oct 2009
    Walhalla, ND
    2009 ct225 bobcat

    Default Re: Bobcat skidsteer 643

    Hi, I've got a 643, had a similar problem. There are 2 metal hyd lines running under the coupler between the engine & hyd pump (main pump). Extremely hard to see & impossible to replace.
    I had to remove the engine to replace the lines. When running/operating oil would pump out of a wear/rust hole in the metal line. (It was a very small hole, but under pressure let out alot of oil) After shut down for the night it would run out all over the shop floor. I removed about an 1" of muck from under the engine when I pulled it out.
    It's a bugger of a job, but removing the engine & replacing it isn't really that bad, I did it mostly by myself with help of a platform lift jack. Cost was about $140 for the 2 new lines, + hyd oil, Anti freeze, etc......

    It's a real good time to replace the universal joint between engine & pump, when you do this. I replaced mine, they are spendy$$ though.

    Good Luck.

  3. #3
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Bobcat skidsteer 643

    Paul, welcome to TBN, I have the same problem with my Case 1845C.

    Have you tried the black light and florescent dye in the hyd fluid. You simply add the small container to the hyd fluid, and run the engine/pumps for a while. and shut it down. Then shine the black light all over the inside, hoses, pumps, fittings. There are glasses that come with the kit to enhance the visual detection of the leak. When you see fluid that fluoresces, your leak is there or close by. If there is a trail of fluid, follow to the source. After you find the leak and replace the part, you need to pressure wash the pump,hoses, etc,with detergents to remove all dye from every thing. When finished cleaning, you should be able to see any new leak, after running the machine.

    You might be able to use one of those USB cameras to see up in there.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  4. #4
    Silver Member
    Join Date
    Jan 2002
    Cleveland GA
    varies never keep one long enough to post here lol

    Default Re: Bobcat skidsteer 643

    The metal lines the other poster reffered to is most likely your problem. However you can put a regular rubber hydraulic hose from the fitting at control valve routed under the engine oil pan to the fitting in the left upright. May be difficult to determine which one is leaking (by yourself) I usually just replace both of them, if one has a hole the other cant be far behind.

  5. #5
    Veteran Member
    Join Date
    Dec 2009

    Default Re: Bobcat skidsteer 643

    My 620 may be similar not sure,but I just recently seen the seal where it couples between engine and hydro pump is leakin and that was hard to see.(seal pump shaft, and of course when engine is off no problem) I have been waiting for global warming to get going in this area so I can get it replaced!

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