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Thread: Weird coolant leak...

  1. #1
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    Weird coolant leak...

    I already posted about this in the "random questions" thread, but I thought I'd start a thread so it's easier to find in case this happens to somebody else.

    Basically, I found a small puddle in front of the car, figured out it was coolant, but couldn't any obvious leak under the car. I posted in the random questions thread, and confirmed I should drop the plastic belly cover, and that I should check the radiator, water pump, expansion tank, and the aux fan temp sensor o-ring.

    I jacked the car up, put it on stands, dropped the belly pan, and couldn't see much other than dried crusty drips in a few places, including all over the bottom of the sway bar. It looks like it's all coming from above. Looks like it's the expansion tank. I'll post pics from Tapatalk in the next post so you can see what I'm looking at.

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Wasatch Chapter #504522
    Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2007 BMW X3 Alpine White

  2. #2
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    That's neat. Tapatalk won't let me post a photo. It appears to be totally broken.
    2004 ZHP Vert - Titanium Silver 6MT
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  3. #3
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    Just a few drips here and there...







    Ah-ha... I saw a few drops here when I glanced, but didn't see the crusty coolant pooled on top of the expansion tank...





    I still wasn't clear where the actual leak was from though so I fired it up for five minutes and brought it up to operating temp. Temp held steady. Looked at the tank again and saw this...



    Looks like a pressure relief or something.

    So, new expansion tank? Should I just do a cooling system refresh at the same time? The serpentine belt is original so I assume the other one is, too. The lower radiator hose is a Napa, but the upper looks original.

    Thoughts?

    Thanks!

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Wasatch Chapter #504522
    Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2007 BMW X3 Alpine White

  4. #4
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    Looks very familiar to one I used to have. With the car fully warmed up after driving a bit, turn it off and take a good look around the filler neck of the expansion tank, you may see some slight bubbling, and hear a fizzing noise like air escaping. Right where the neck creases to form the tank... I developed a hairline crack on mine.

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  5. #5
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    That's the air bleeder. when you do cooling system maintenance and refill the system, use open that bleeder to bleed off the air as you fill it with coolant. It's easy to over tighten that bleeder and it develops a crack.
    If you don't know the age of the expansion tank, it may be a good time to swap it out for peace of mind. Otherwise just replace the bleeder screw and see what happens...
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  6. #6
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    You could also borrow/buy a pressure test kit to pump some air into the system and see where the leak actually is, but I agree with Rob.
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  7. #7
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    I have no doubt the expansion tank is the original, so it's 45k miles and 12 years old. Like I said earlier, I definitely want to do a complete cooling refresh at some point. The kit with tank, hoses, pump, and belts at ECS is only $300-some dollars, so it's a no-brainer.

    That said, I'd like to wait and do that this winter if possible so I can use the car now. So, would you guess the vent screw is what's developed a leak? Looking at Real OEM, that's a separate part...

    http://www.realoem.com/bmw/enUS/part...&q=11537793373

    Should I just pick one up at the dealer if they have one and try it?

    Just hoping to drive the car this weekend instead of spending the whole weekend working on it or leaving it parked until I can order all the parts for a whole refresh.

    As always, thanks guys!!!

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Wasatch Chapter #504522
    Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2007 BMW X3 Alpine White

  8. #8
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    I did my cooling system at 49k miles due to age rather than mileage. The components were about 10 years old at that time. If the leaking's not significant beyond the bleeder screw, which you can replace as you stated above, then I would think you could hold off until the winter or at least the fall.

    As for replacement kits, I recall Vas not having a great experience with ECS' kit. I went with Turner Motorsport's kit and haven't had any issues. If I were to do it again, I would look up all the individual part numbers through RealOEM and then price it out as cheap as possible through FCP and ECS.

  9. #9
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    Quote Originally Posted by BMWCurves View Post
    I did my cooling system at 49k miles due to age rather than mileage. The components were about 10 years old at that time. If the leaking's not significant beyond the bleeder screw, which you can replace as you stated above, then I would think you could hold off until the winter or at least the fall.

    As for replacement kits, I recall Vas not having a great experience with ECS' kit. I went with Turner Motorsport's kit and haven't had any issues. If I were to do it again, I would look up all the individual part numbers through RealOEM and then price it out as cheap as possible through FCP and ECS.
    Sweet! Good to hear! Thanks for the help!

    Definitely want to do the cooling system refresh. It's a 12-year old car, and there's just so much plastic in these cars now. It just makes sense. But, it's supposed to be sunny and in the mid-80's here tomorrow, so I just want to drive the car. Plus C&C on Sunday morning!

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Wasatch Chapter #504522
    Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2007 BMW X3 Alpine White

  10. #10
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    The dealer has the screw for $5 or whatever. I was just there yesterday buying coolant. Here's a trip that requires $5 in gas to buy a $5 part. Doh.

    That said, googling "bmw vent screw leak" yielded 163,000 results, so apparently this isn't very weird. Hindsight.

    SC
    2004 ZHP Vert - Titanium Silver 6MT
    BMW CCA Wasatch Chapter #504522
    Daily Driver: 2007 Hummer H3 Adventure * Wife-mobile: 2007 BMW X3 Alpine White

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