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Thread: Coolant Expansion Tank Gasket Replacement

  1. #1
    Join Date
    Jan 2008
    Location
    Irvine, California
    Posts
    17
    My Cars
    335i Coupe 6-speed

    Coolant Expansion Tank Gasket Replacement

    I have a consistent leak that appears to be the gasket on the Coolant expansion tank.

    Looks inexpensive to replace the whole reservoir by buying one online ($80 for OEM, or $120 for bmw parts) or even cheaper to buy a new gasket ($4) for it. Anyone ever just change the gasket? Curious of any gotchas to look for when doing if I go that route.

    See pick below as it shows some of the leak. Actually gets worse the warmer the engine gets.

    Screen Shot 2022-04-28 at 6.27.53 PM.png

  2. #2
    Join Date
    Mar 2020
    Location
    Martellago, Venice, Italy
    Posts
    8
    My Cars
    2006 e91 bmw 320d msport
    You need to replace all the reservoir.
    The gasket many time don't resolve the problem because the reservoir tend to deform over time.
    Are you sure there isn't an overpressure in the sistem?

    Inviato dal mio Redmi Note 9 Pro utilizzando Tapatalk

  3. #3
    Join Date
    Jan 2008
    Location
    Irvine, California
    Posts
    17
    My Cars
    335i Coupe 6-speed
    What would be too much pressure?

    The bubbling does worry me (in my picture) though I hope it's just the cap or the expansion tank that's the issue. I do see some moisture in that gap looking around the expansion tank. Going to buy a pressure kit to see if there are any other leaks.

    Assuming I can use that tool by turning on the engine to see if the pressure increases to see if there's too much pressure?

  4. #4
    Join Date
    Mar 2020
    Location
    Martellago, Venice, Italy
    Posts
    8
    My Cars
    2006 e91 bmw 320d msport
    Pick a latex glove.
    Put It on the reservoir with a Rubber band instead of the cap
    Start the engine (engine cold).
    If in one minute the glove start to inflate, there is a head gasket leak.
    Otherwise Is a reservoir leak

    Inviato dal mio Redmi Note 9 Pro utilizzando Tapatalk

  5. #5
    Join Date
    Jan 2008
    Location
    Irvine, California
    Posts
    17
    My Cars
    335i Coupe 6-speed
    Was a reservoir leak. Just replaced the expansion tank and everything was fine again and no more leaking.

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