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Thread: Coolant leak! Back of engine, need help

  1. #1
    Join Date
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    Question Coolant leak! Back of engine, need help

    Hi Guys I bought a 2005 BMW 545i about 2 years ago. Car always gave out the low coolant light ever few months but lately it has been loosing coolant rather quickly.
    I have replaced the expansion tank w/cap, and the front hoses.

    Today I went underneath the car, took out the metal shield and saw slow coolant dripping down between engine and transmission on the driver's side. I could not view anything on the top side of the engine due to very limited view but it seems to me the leak is coming from back of the engine.
    There is no leak of the coolant inside the car. I am not sure how to tackle this? do I have to remove the intake manifold to see anything in the back side of the engine?

  2. #2
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    Bmw 545i coolant leak from the back of engine, need help

    2004 BMW 545i, purchased about 2 years ago.

    My coolant low light has been going off for few days now. Today I went underneath the car and checked everything thoroughly. After removing the plastic and metal engine shields,
    I noted slow dripping of coolant on the DRIVER's side between engine and transmission. The space is very limited to look at anything with a clear view but it seems like the coolant is leaking from the back top side of the engine.
    I did not notice any leak inside of the car.
    Now I am worried if it is heater core/hoses or something else. I can't even look a the hoses properly because of limited view. Do I have to remove the intake manifold?
    Please help.

  3. #3
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    Either the valley pan is leaking or the plate on the back of the engine block that connects the coolant passages in the block together is leaking, if this leaks the coolant would come out of the inside of the bell housing to repair this the transmission and flywheel need to be removed. If it was the valley pan the coolant would be running down the outside of the bell housing and if you look under the intake manifold you might see coolant pooling up or it could be heate hoses. But since it is so hae
    Last edited by jclausen; 12-23-2018 at 11:55 AM.

  4. #4
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    I did a pressure test last night. Coolant was dripping like crazy from back top of the engine. It is flowing from top of the bell housing downwards on the drivers side. Its not leaking from the inside of the bellhousing.

  5. #5
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    Well that's good news, I would look under the intake manifold at the valley pan plate. Might need a mirror and a flash light

  6. #6
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    I tried by best to look but cannot see anything. All I can see is the right side of bell housing is wet from the top. I cant see anything in the back side of the engine even with mirror.

  7. #7
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    Your going to have to remove covers get a flash light and a mirror or just have a shop pin point the leak

  8. #8
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    Sounds like the valley pan to me.
    ASE and BMW Master Certified Technician

  9. #9
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    Yea

  10. #10
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    Question

    What are the signs of rear seal leaking of transfer pipe? or should I just replace the valley pan gasket?

  11. #11
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    You mean the pipe under the the valley pan, if it is leaking there was a weep hole on the drivers side of the timing covers that would be leaking. This engine does not have a transfer pipe like on the earlier e38/e39 v8's that would be attached to the back of the clyinder heads. The coolant moves from the back of the heads thru the plate that is mounted behind the flywheel.
    Last edited by jclausen; 01-07-2019 at 10:19 AM.

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