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Cold engine coolant air pockets?

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    Cold engine coolant air pockets?

    As I'm finishing up my 2.7i turbo on a completely refreshed engine, I filled it up with coolant and planned to start it up when I get done wiring up the GM coils. This morning I wake up to a text from my woman telling me that my car in the garage is leaking and I walk out to find a small puddle of coolant near the driver's frame rail on the ground. As I'm searching frantically to find where this leak is, I can't find any evidence from the hoses attached to the heater core, the thermostat, let alone anything that is attached to the engine. I had to go to work so I just cleaned up the coolant.

    I went home on my lunch break to get a second (and less groggy) look at it. Thinking in relation to where the coolant was and no signs of leaking anywhere in the engine bay, I pulled the overflow hose from the fender and low and behold...signs of it going through that tube.

    Cool! Found the problem. Only thing that boggles my mind is how it managed to escape from the expansion tank despite the engine never running. I merely opened the bleeder screw, filled up 2 gallons of BMW coolant (50/50 mix, of course) until coolant came out of the bleeder hole, and topped the tank off and put the cap on and called it a day. The only logical reason behind that happening is possibly air in the cooling system.

    Has anyone else come across this? This is certainly a first for me. I'm going to fill it back up tonight to see if the problem replicates and report back.
    1989 325i - 2.7i, Holset H1C, 60lb injectors, whodwho MS-PNP.
    2012 Passat TDI - DD Duty
    2008 GMC Yukon XL Denali - Kiddie hauler/grocery getter

    #2
    If the expansion tank weas overfull it can leak out of the overflow hose. You absolutely have air in your system as you have yet to start the car, get it up to operating temp, and allow the thermostat to open. You could pull the upper radiator hose and pre-fill the radiator, that will reduce the amount of bleeding you need to do while running.

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      #3
      Jlevie has posted a proper bleeding procedure at least a dozen times...

      Comment


        #4
        Originally posted by dnguyen1963 View Post
        Jlevie has posted a proper bleeding procedure at least a dozen times...
        I don't have an issue bleeding the cooling system. I'm fully aware of how to do that. I was concerned with how or why it did it and CorvallisBMW explained it spot on (at least from what I have gathered).
        1989 325i - 2.7i, Holset H1C, 60lb injectors, whodwho MS-PNP.
        2012 Passat TDI - DD Duty
        2008 GMC Yukon XL Denali - Kiddie hauler/grocery getter

        Comment

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