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Thread: Z4 coolant/heater issue

  1. #1
    Join Date
    Mar 2019
    Location
    Leicester england
    Posts
    1
    My Cars
    BMW Z4 2.5

    Z4 coolant/heater issue

    After owning my 03 88000miles z4 now since last summer, I have been fixing bits n Bob's and now it drives sweet !
    Last few wks thow the coolant low has been popping up intermittently, kept checking level and cant say its losing much /if any , so led me to think it's a bad sensor which I was going to get round to sorting when it gets a little warmer, however , the heater in the car now seems to take longer to get up and is also blowing hot/cold wich is new . After googling leads etc it cant be thermostat as the temp gauge on dash is fine sat in middle, car has never over heated so I dont know what the hell this could be
    Coolant low indicator ... on and off
    Temp gauge .............. . . Fine
    Coolant level ........... Fine
    Heater ....... takes ages and then blows hot n cold randomly



    Any help on this guys is really appreciated as it's a real head scratcher and I'd like to identify the problem before it causes anything else. Thanks

  2. #2
    Join Date
    Jan 2015
    Location
    Timaru, New Zealand
    Posts
    1,132
    My Cars
    Two Z3 Roadsters
    Sounds like an air block in the heater system. But where did the air come from?? An air block will cause the heat to take longer to come, then be hot when the rev's are up (driving) and cold when the engine is at idle (stop lights). Does this match your random pattern?

    The temp gauge is dampened in the middle range, so using it to pick a definitive temp change is a waste of time. Use a scanner to monitor engine temp. It should be around 96*C.

    If you are worried about a blown head gasket, get the engine checked by a mechanic. There is a product that can be put into the cooling fluid that will tell you by colour change if their is combustion gases getting into the cooling fluid.
    1999 2.8L Z3 Roadster,
    2000 3.0L Z3 Roadster,

    There is only one thing more pleasurable than working on a Z3, that's driving it top down on a fine day.

  3. #3
    Join Date
    Sep 2007
    Location
    Bellevue, WA
    Posts
    1,434
    My Cars
    2004 Z4 3.0i
    You most likely have a small leak somewhere in the system, this literally JUST happened to me. Original leak was coming from my expansion tank and then after I changed the tank found more leaks coming from thermostat area. I replaced thermo, waterpump, and expansion tank, flushed coolant and bled, and now all is well in the world. Well as far as my cooling system goes anyways.

    You are right at the mileage where all of those components are about to fail anyways, might as well get it done on your terms instead of getting left stranded on the car's schedule. I think the whole thing cost me less than $300 in parts.

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