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Thread: Unidentified Oil Leak 2007 750Li

  1. #1
    Join Date
    Mar 2007
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    2003 E39; 2007 E66

    Unidentified Oil Leak 2007 750Li

    Guys and Gals

    My 2007 BMW 750Li is leaking a clear 'light film' oil from the front middle right side of the car. Started about 6 weeks ago and getting progressively worse. I am attaching some pics where the oil leaked on some cardboard. Hoping to get some pinpoint ideas. This is not motor oil, feels more like a light hydraulic oil of some sorts.

    Any help is appreciated...

    IMG_0782.jpg

    IMG_0783.jpg

  2. #2
    Join Date
    Dec 2007
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    '93 850Ci- Daily Driver
    I would start by thoroughly power washing the engine bay and underside to get all the dirt and grime off. Once you have done that, the leak should be real easy to pinpoint - it is difficult to see over the internet otherwise.
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
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  3. #3
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    I would highly advise against pressure washing the engine bay. Besides, unless the leak is right on top, you're not going to do anything but wash down a bunch of crud, making it harder to find the leak from underneath.

    Start with the basics. If you're sure it's not engine oil, then the only two other options are power steering fluid (your car uses Pentosin CHF11S), or transmission fluid. Have you checked the fluid level in the reservoir for the power steering? 11S is green when it's fresh out of the bottle, but the color lightens with age. The most common sources of hydraulic fluid leaks would be the pump itself, or the active sway bar. The valve block is right behind the front right wheel, but I've never see one leak. There are hard lines, rubber lines, and some braided lines that run all over the engine bay, and in/around the front frame. You're just going to have to get under the car, take off the belly pans and search for the leak.

    The tranny typically only leaks from the pan and/or the sealing sleeve (where the electrical connector goes in). These would be under the center of the car, not directly under the engine bay.
    ASE and BMW Master Certified Technician

  4. #4
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    '93 850Ci- Daily Driver
    I regularly wash down the engine bay, have been doing it for decades without any problems on all of my cars and trucks. The key to doing this successfully, is to not shoot water directly into electronic components. Get yourself some good engine cleaner (GUNK Brand or similar and follow the instructions on the bottle), wait the 15-20 minutes and have at it. Not only does it make ANY leak immediately noticeable, but it also keeps it relatively clean to work on.

    Also, PENTOSIN is green straight out of the bottle as you stated, but starts to turn towards a darker brown when it is older and dirty - looks more like thinned engine oil.
    '93 850Ci - Mineralweiß Metallic

    2001 740iL - Titansilber
    ALPINA B7 -Alpinweiß III


    ...the price of cool ain't cheap!

  5. #5
    Join Date
    Jan 2016
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    Ca
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    2001 525it
    Passenger side of the engine, right valve cover & upper timing cover gaskets, vacuum pump. Oil pressure switch. The three most common things or active sway bar system leak, is the fluid low?

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