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Thread: Got the expansion tank out of my 2004 BMW 330xi

  1. #1
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    Got the expansion tank out of my 2004 BMW 330xi

    So I finally got the expansion tank out. When I put in the new tank I had a suspicion something wasn’t seated right. Sure enough when I reconnected everything and poured in some coolant a steady flow came out the bottom. I am thinking the small thermostat below the tank isn’t seated in correctly or the tank isn’t all the way down. How can I tell if the thermostat is seated in correctly? Thanks for any help.

  2. #2
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    When replacing the plastic expansion tank we replace the plastic mounting plate and hardware since all the plastic is the sam age and brittle and brown. Also use some silicone on the rubber seals so things go together easier.

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  4. #4
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    Hi. I believe I got the thermostat seated in correctly as it clicked. I poured in some water and it is leaking out. I could be wrong but seems like its coming from that smaller tube that comes out next to the wider one that covers the thermostat.

  5. #5
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    Double checked the housing covering the thermostat is dry.
    The coolant level sensor area is dry also. It’s that other tie that’s leaking. On the old expansion tank there was an o ring in there. I am assuming the new one also had that?

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    Not to be funny, but it's seated correctly WHEN IT DON'T LEAK!

    Quote Originally Posted by Shumanfoo View Post
    So I finally got the expansion tank out. When I put in the new tank I had a suspicion something wasn’t seated right. Sure enough when I reconnected everything and poured in some coolant a steady flow came out the bottom. I am thinking the small thermostat below the tank isn’t seated in correctly or the tank isn’t all the way down. How can I tell if the thermostat is seated in correctly? Thanks for any help.
    Sorry again, that's the only way to tell. You might have checked it for leak before ¥ou installed it in the car. So remove the tank and check it out of the car with straight water...

  7. #7
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    I had to replace mine also. It still leaked and turned out to be from the o-rings on my hoses even though they looked fine and felt like they seated when connected. I bought new hoses and my problem went away. Just my $0.02.

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