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Thread: Coolant level drops fast

  1. #1
    Join Date
    Mar 2013
    Location
    Alpharetta
    Posts
    113
    My Cars
    1998 z3

    Coolant level drops fast

    I know this has been covered numerous times but I'm baffled. Sons 96 e36vert has to have the coolant reservoir completely filled every couple weeks.

    No Symptoms, none on the ground, new reservoir, no coolant smell, no white exhaust, no coolant in oil, no leak from fairly new water pump. Had it pressure tested awhile ago.

    I could live with topping it off on occasion but this stuff has to be going somewhere.

    Ideas please?





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  2. #2
    Join Date
    Jul 2010
    Location
    Murrieta, CA
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    9,530
    My Cars
    '94 325iC, '08 328i, E93
    IF your trouble is a cracked head, you would have all of the symptoms that you list -- no smell, no puddles, no coolant in the oil, and so on.

    If you were to remove the head and turn it belly-up, the #3 and #4 cylinders have a thin wall between one of the exhaust valves and the adjacent water galley. Tiny amounts of coolant pass from the water jacket (passage) into the exhaust stream where it is vaporized. I'm not suggesting you tear the engine down, but if you were to do such a thing then you want to inspect very closely the wall between the exhaust valve seats and the adjacent water passage. I believe this picture is the #3 cylinder, but the 3 and 4 ought to be mirrors of each other so the trouble could be either or both, 3 and/or 4.

    BMW - Cracked Head.jpg

  3. #3
    Join Date
    Jul 2008
    Location
    Baton Rouge, LA
    Posts
    940
    My Cars
    '98 328i convertible
    Is the reservoir completely empty?

    Filling the reservoir completely is not the correct thing to do. Once the engine heats up, the coolant will expand and push coolant out of the system as needed. When it cools back down, the reservoir will have a lower level in it. But it should not be empty.
    - Ken -

  4. #4
    Join Date
    Jul 2010
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    '94 325iC, '08 328i, E93
    Also, this is not really a question that is unique to the convertibles. It's a common problem for the Inline Six engines of all chassis configurations.

  5. #5
    Join Date
    Apr 2010
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    United States
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    My Cars
    02 525,01 X5,99 323IC
    I have had 2 of these engines have cracked coolant passages just like the above pictures. As the corrosion/cracks grow you will also start to pressurize the coolant system and start to blow hoses. So, be prepared for that! Keep an eye on it closely.

  6. #6
    Join Date
    Jul 2010
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    Murrieta, CA
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    '94 325iC, '08 328i, E93
    Quote Originally Posted by capebmw View Post
    I have had 2 of these engines have cracked coolant passages just like the above pictures. As the corrosion/cracks grow you will also start to pressurize the coolant system and start to blow hoses. So, be prepared for that! Keep an eye on it closely.

    What happens is that as the coolant loss becomes greater, the engine temp rises which produces more pressure. System Pressure is a function of temperature. Less coolant = more temperature = more pressure.

  7. #7
    Join Date
    Sep 2007
    Location
    SF Bay Area
    Posts
    548
    My Cars
    98 M3 vert, 05 X5
    I "love it" when someone starts a thread, asks for help, then never returns to read the comments members take the time to leave for them...!

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