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Thread: Bad water pump, affecting bleeding cooling system???

  1. #1
    Join Date
    Sep 2015
    Location
    bay area, ca
    Posts
    7
    My Cars
    2003 745li

    Bad water pump, affecting bleeding cooling system???

    Hey fellas... been trying to solve this problem for a while now...

    I have a 2003 745Li. I have redone the whole cooling system besides the radiator and the water pump. I was wondering if a bad water pump would affect me bleeding the system completely and getting all the air out of it? The coolant leaks out of the cap after i drive for a while... mostly when I'm in stop-and-go traffic, the cap starts to spit coolsnt out of it which leads to overheating. After draining all the coolant out my car, i was only able to add about 8 liters (i didnt drain the block) the system holds pressure well but it seems like there's a lot of air in there cause when I open the cap I hear a lot of air coming out. When bleeding the coolant system, i hear the electric water pump turning on, but just wondering if just cause i hear it, does that mean its working properly

    I also want to add I need a new alternator as the volts are really low I have a electric water pump thinking maybe that has something to do with it any advice is greatly appreciated thank you
    Last edited by beatitdown707; 05-25-2017 at 12:24 AM. Reason: To be more clear

  2. #2
    Join Date
    Feb 2009
    Location
    KC North, MO, USA
    Posts
    11,153
    My Cars
    1996 740iL
    Moved to model sub forum.

  3. #3
    Join Date
    May 2017
    Location
    USA
    Posts
    159
    My Cars
    E90, E46
    Your 03 does not have an electric water pump it is mechanical. it sounds like your overheating or over pressurizing.
    when our system gets too hot/too much pressure it will vent from the cap.
    Check your thermostat? Possible head gasket issue?

  4. #4
    Join Date
    Sep 2015
    Location
    bay area, ca
    Posts
    7
    My Cars
    2003 745li
    Come to find out my fan clutch was also bad... so would a bad fan clutch make my car over heat and cause the coolant to come out of the expansion tank top???

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