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Thread: E39 still over-heating after complete cooling system overhaul.

  1. #1
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    E39 still over-heating after complete cooling system overhaul.

    I have a 1998 528i.
    About a month and a half ago I had to replace the water-pump, so while in the process I decided to give my car a complete cooling system over-haul. I replaced the radiator, fan, fan clutch, t-stat, hoses, ect and my car began over-heating at idle... which is a nightmare during traffic or at stop lights.
    I bled the cooling system correctly more than once [according to this forum]. I have no white smoke, no sweet smell, no milky residue under my oil cap or on my dip stick and no leaks and my radiator hose is not rock hard after drive.
    So, before I spend money getting a over-priced diagnostic at BMW, I wanted you guys' opinion on what the problem could be.

    any ideas?

  2. #2
    323i E30's Avatar
    323i E30 is offline ⅂!ʈө !ƨ l!ʞө ɐ ʇөlөbµouө
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    My guess would be that your new T-stat doesn't function properly.

    When the engine is at operating temp, check if your driverside hoses from the radiator are hot. They should be as that means that your Tstat is open.
    Note that this is the case at an E30, and I have no experience with E39s, but I figure it will be the same...

  3. #3
    Join Date
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    2001 BMW 530i
    Quote Originally Posted by 323i E30 View Post
    My guess would be that your new T-stat doesn't function properly.

    When the engine is at operating temp, check if your driverside hoses from the radiator are hot. They should be as that means that your Tstat is open.
    Note that this is the case at an E30, and I have no experience with E39s, but I figure it will be the same...
    Sounds reasonable. I had a t-stat put in my e39 and it went bad 2 weeks later. The repair shop put in a new one for free (under waranty). The tech said the new plastic t-stats actually work better than the metal ones. I still wonder about this but my plastic one hasn't failed yet "?" (going on 1 year)
    2001 BMW 530i e39 / Automatic / Orient on Dove

  4. #4
    Join Date
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    '15 MB GL
    I've jacked up front ends to bleed systems, jacked up the rear, upper hose bleed, bleed from water pump on the 2nd tuesday between noon and 1:15 ...


    Find a garage with a power vacuum fluid replacement machine, I'm willing to bet you still have an air pocket in the lower section of the cooling system, assuming the new parts are installed properly.

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