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Thread: HELP! Coolant leak at under carriage!

  1. #1
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    Exclamation HELP! Coolant leak at under carriage!

    Hello Bimmerfest family,

    Recently, my 12'-550i started needing the coolant reservoir filled once a week. You can definitely smell the heated coolant after a day of driving. I initially thought it would be the typical turbo lines, but upon inspection - nothing... Had a mechanic run a coolant vacuum test and he noticed that what appears to be somewhere where engine and transmission meet there is a large leak. Does anybody know why this area would have coolant coming from it? I attempted to attach a photo to this post, but don't know if would come through. Currently, I am filling it up weekly to avoid any critical failures. Any of your feedback would be greatly appreciated. Thanks!

    Mel

    Photo link: https://drive.google.com/open?id=0B5...Eg3aVpvdkZtdkk


  2. #2
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    The turbo coolant and oil lines are easy to see at the top but disappear down into the v of the engine. Coolant leaking in the v would probably come out the back, like when the oil hose return plate leaks. Look down in the v with a bore scope. It's pretty hard to see anything in that engine compartment

  3. #3
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    Wow! Thank you jclausen! I will try towards the end of the week... Not sounding like an "idiot"; is a bore-scope something you can get a local auto parts store? Thanks again and I'll keep you posted... many thanks!

  4. #4
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    A bore scope is a camera or viewing screen with the lens at the end of a metal fixable tube, so it fits in to spark plugs holes nicely for instance. The camera or screen part is what is in your hand. A lot of shops might have them. One of my techs bought one on eBay pretty cheap, he can use his phone for viewing. Good for looking into tight places

  5. #5
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    Thank you! Found one in Amazon and hoping to get soon... I'll let you know outcome(s). Take care...

  6. #6
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    There are about a dozen lines that carry oil and coolant to and from the turbochargers on your engine, they are all prone to failure and are a consumable item IMO. Typical in-service interval is about 75k between needing complete overhaul due to excessive leaking. There is a drain hole at the back of the valley the turbos sit in that allows the leak to drain down the back of the block and often is first noticed where pictured. There is also a distinct possibility looking at your photo the rear end cover on the block is leaking, which requires removal of the transmission to replace.

    I service these pretty routinely if you'd like it looked at my a BMW specialist.

    Good picture of the end cover:






    Another picture, where you can see the coolant leaking down over the end cover *from* the weep hole that drains the valley:


    To compound matters further there is a design flaw with the rear cover plate that allows oil to leak and it is not repairable with the standard factory issue replacement end cover, and requires the use a a "skunk works" AGA privately made for BMW billet end cover to resolve.
    Last edited by Stück; 09-11-2017 at 08:53 PM.
    Tenured Automotive Service Professional - Avid BMW Enthusiast

  7. #7
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    Wow - thanks Stuck...

    This can be pretty serious, huh? I assume this is a critical failure and continuously refilling the coolant may come to a point these parts will simply give out. It also seems this is not covered by BMW being a 2012 new 72K miles. I may have to bring to BMW specialist like you mentioned to see cost to fix... sigh...

  8. #8
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    I totally for got about the plate back there

  9. #9
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    The most likely cause would be the coolant vent pipe. It's behind the alternator, down below the front of the turbo's. The plastic "Y" fitting cracks and leaks. This coolant then runs out the weep hole at the back of the engine. Check this hose first. If it's original, replace it anyway. They break in half just by looking at them.

    The second possibility is the coolant rear end cover on the back of the engine block behind the flywheel.
    ASE and BMW Master Certified Technician

  10. #10
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    @jclausen, @Stuck, @White94RX

    Sorry to bother you guys, but I "think" I encountered another problem. Last weekend, drove the car a little more aggressively and the coolant light came on needing a refill. I had coolant in the trunk and emptied the whole container into the Coolant Reservoir. Strangely, it emptied as fast as I was able to fill it.

    I made it home and let the car cool. Later on the week, I tried refilling the coolant reservoir thinking it may have been a "leak" in the reservoir itself. Same thing where it literally emptied as fast as I can fill out. Strangely, I knew it was going to be a leak and I look under the car on a dry driveway and NO LEAK found anywhere! Wow! It was a like a magic trick.

    Any idea where the water is emptying? I start the car and it "sounds" fine at idle, but don't run too long due to lack of coolant. Your ideas to locate leak, capable of DIY fix and guidance is all greatly appreciated.

    Many thanks,

    Mel

  11. #11
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    Not much you can do except take off the underbelly panel to find the leak. The underbelly panels are very absorbent as well and can hide leaks.


    Sent from my iPhone using Tapatalk
    ASE and BMW Master Certified Technician

  12. #12
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    Thanks White94RX... It sure is a "mystery"...

  13. #13
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    You need to have the cooling system inspected it would a real bummer if the engine overheated and got damaged.

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