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Thread: Trying to diagnose a slow coolant leak 2001 325i

  1. #1
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    Trying to diagnose a slow coolant leak 2001 325i

    2001 325i

    So this coolant leak has been around for quite a while, it's slow enough that I've just been putting up with it. I falsely diagnosed it as the classic expansion tank issue, replaced that, but that didn't solve it. I also recently replaced the water pump, but the leak was happening before that and the replacement didn't effect it (though the pump was definitely done).

    I think the leak is coming from the top of the radiator itself, which I'm guessing just means I have to replace the whole radiator, but I'm trying not to repeat my expansion tank mistake.

    So some pix - here's the most visible drip, but I've looked all around this drip and it seems pretty dry, I'm fairly certain it's coming from much further above:
    IMG_0490.jpg

    Here the left side of the radiator, just in front of the expansion tank. You can see coolant pooling on the three "lips" (for some reason this pic is rotating 90 degrees left when I post it)...
    IMG_0481.jpg

    And here's the top of the radiator (also just in front of the expansion tank) (again the forum is rotating this 90 degrees left bizarrely)
    IMG_0482.jpg

    Here's roughly where I think it's coming from, but not 100% sure...
    IMG_0489.jpg
    Close up:
    IMG_0488.jpg

    Any ideas (also any ideas why this images are getting rotated??)

  2. #2
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
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    The radiator is a 10 year replacement item, as the plastic to aluminum seal goes bad over time. Can you stretch it out to 15 or in you case 18 years, I wouldn't.

    I am assuming that you are using a pressure test to see the coolant coming out of those location, and you can get a replacement off of Amazon for around 150 bucks if you have a manual transmission.
    Darin
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  3. #3
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    To add to Darin’s excellent advice, you need to overhaul the entire cooling system!! That means:
    - water pump (Saleri or Graf)
    - thermostat (Whaler)
    - upper and lower hoses (Continental)
    - serpentine belt (ditto)
    - idler and tensioner pulleys (INA)
    - radiator (Nissen or Behr)
    - expansion tank (Modine ONLY)
    - expansion tank bracket (?)
    - expansion tank cap* (?)
    - sensor in the lower radiator hose (likely VDO)
    - engine block coolant drain plug crush washer (dealer)
    - coolant (BMW ONLY)
    - distilled water.

    * Buy a 1.4 bar (1 bar = 14psi; 1.4 bar = ~20psi) cap instead of the 2 bar (28psi) cap that cane with the car. Why? This prevent the cooling system from getting too high. I’d did this in my old 330Ci and never regretted it. Buy the parts at FCPEuro as the vender provides a lifetime warranty on all parts.

    Do not piecemeal the replacement of cooling system parts. Just do it all at one time.

  4. #4
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    So sounds like you think it's just the radiator and a replacement will solve it? I'm happy to replace it, just don't want to repeat my expansion task mistake if there's some other possible culprit I'm missing.

  5. #5
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    Just replace it. If it's original, it's past due anyhow. Many don't last much more than 10 years.
    Quote Originally Posted by B4SH View Post
    If anyone knows, it's this guy who knows literally nothing about everything.
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  6. #6
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
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    Yes, it is time for the radiator to be replaced. Have you replaced the surge tank carrier yet? Typically I do those at the same time the radiator is getting replaced.

    Also as a side note, if you are having a hard time getting the O-Rings to seal, use a little bit of dielectric grease on them.
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

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