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Thread: Radiator cooling circulation test

  1. #1
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    Radiator cooling circulation test

    Hello
    I have a 1981 BMW 320i , 4 cyl. , auto .
    The radiator bottom hose clamp that connects to the thermostat housing broke (old and rusted) and leaked coolant , The clamp was replaced and new coolant was added to fill the radiator . The engine was started to get the air out of the system and check for leaks . No bubbles and no leaks after 10 or 15 minutes , with out the radiator cap , however , I noticed NO COOLANT CIRCULATION , the coolant temperature reached normal level , but , no coolant circulation . Radiator top was not warm , coolant inside radiator was not even warm , engine temperature feels OK ( with hand touch) , SO ???? ,
    I want to check if there is the correct coolant circulation , because the coolant inside the radiator was still , no movement at all .

    [SIZE=4]Any suggestions on how to check circulation ????

    Please advice , thanks

  2. #2
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    Have you tried with the heater valve closed?
    Tbd

  3. #3
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    Hello
    The heater valve is not in service or works , at present

    Please advice

  4. #4
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    Quote Originally Posted by luis320i View Post
    Hello
    The heater valve is not in service or works , at present

    Please advice
    Do you mean the heater valve is missing, and/or bypassed with a hose? Or is it stuck shut, or stuck open?

    Reason I ask is because if the heater valve is 'open', or bypassed with a hose, then most of the coolant circulation will not make it's way through the main radiator, especially at slower engine speeds.
    Last edited by epmedia; 03-13-2019 at 03:45 AM.
    Tbd

  5. #5
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    Hello
    The heater valve is not in service or works , at present .
    Sorry , what I was trying to say , the valve control knob in the dashboard is not working , so I do not know if it is "open" or "close" , can you tell me where is this valve located ??? so I can check , and , as I understand you , it should be open , in order to sen the coolant to the main radiator . Am I correct ???? , If you have any other suggestions to check and or verify , please let me know.

  6. #6
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    I have this saved on my computer but I don't know the source. It looks out of the Factory Service Manual but this page isn't on the PDF version I have.

    coolant-cycle-m10.jpg
    '81 E21 320i / '90 E30 325i / '̶9̶2̶ ̶E̶3̶4̶ ̶5̶2̶5̶i̶t (sold) / '15 Toyota XW30 / '̶̶8̶0̶ ̶E̶2̶1̶ ̶3̶2̶0̶i̶A̶ (sold)

  7. #7
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    Quote Originally Posted by luis320i View Post
    Hello
    The heater valve is not in service or works , at present .
    Sorry , what I was trying to say , the valve control knob in the dashboard is not working , so I do not know if it is "open" or "close" , can you tell me where is this valve located ??? so I can check , and , as I understand you , it should be open , in order to sen the coolant to the main radiator . Am I correct ???? , If you have any other suggestions to check and or verify , please let me know.
    Incorrect.

    Assuming the heater and heater valve were functional:
    When the heater valve is 'open' (heater on, full hot) the coolant will 'mostly' circulate through the heater matrix (heater core), instead of circulating through the main radiator.

    - - - Updated - - -

    Quote Originally Posted by amarino View Post
    I have this saved on my computer but I don't know the source. It looks out of the Factory Service Manual but this page isn't on the PDF version I have.

    coolant-cycle-m10.jpg
    Ugg, that's hard to follow! eek . lol

    Need a real pic...
    Luis, can you post a pic? the heater valve is sort of next to the brake vacuum booster. You can see two 'heater' hoses going through the firewall, next to that brake booster.
    Last edited by epmedia; 03-14-2019 at 03:46 AM.
    Tbd

  8. #8
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    Whew ...
    definitely hard work to get a picture in situ .. it's a bit fuzzy but hopefully helpful.
    the other one is pretty self explanatory

    Cheers
    Attached Images Attached Images
    hmm .. Wonder what happens if I do this ...

  9. #9
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    79 320/6 81320i 65malibu
    Not saying this is your problem - just a possibility.

    M10 thermostat housings have two thermostats in them, one that is closed when cold and one that is open. The one that is closed keeps the pump from pulling water out of the bottom of the radiator. While the other one that is open lets the pump circulate water in the block, head and heater.

    I had one once that the one that opened to pull water out of the radiator was opening up correctly, but the one that closes when warm was not closing all the way. The issue this causes is over heating after about 5 or more miles at highway speeds. As soon as I slowed down the engine cooled down some. Really took me awhile to figure out - it is easier for the water to circulate in the cold around the block flow path then through the radiator.

    So while it was pulling some water out of the radiator at highway speeds, it was not pulling enough to keep the engine cooled down. But at slower speeds it was enough to cool the engine.
    Last edited by OLD MAN; 03-14-2019 at 09:15 AM.

    Always FUN TO DRIVE - Build Thread & Tech info - 79 320/6 track car build thread -- Videos of track car -Adam in car Auto-x video - Start-up video - 4/2011 Adam's TOP BMW time San Diego BMWCCA - 4-5-15 Dyno break-in run new M20B25 - Exhaust Thread - Link

  10. #10
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    Hello guys
    Thanks for all these information , I will check it tomorrow and see the position of this valve , and make sure it is closed .
    Once , I remove the thermostat housing and cleaned , and tested with hot water and it did worked , how ever , in this area usually the weather is very warm and muggy , and during the summer ambient temperature gets above 100 F almost every day and the cars get very hot , so , I am thinking if would be a good idea to remove the thermostat in order to help coolant circulation . This winter the lowest temp. was 40 F to 50 F .
    Please let me know your thoughts , and I will let you know my results

  11. #11
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    Hello
    I just want to say the epmedia's car looks great .
    Mine looks a lot like epmedia's , and I would like to share my pic with you , but , I do not know how to post it on this forum , I have it my iphone , any suggestions on how to do it ??
    Thanks

  12. #12
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    Hi Luis, thanks. I wish I knew how to do pics from a phone, maybe someone else can help with that.
    Do Not remove the thermostat, because what OLD MAN described. You can get a new thermostat at lower opening temperature instead. Try the 75c (167f) thermostat. Original thermostat: 80c (176f)

    Great pics GDAus!
    Tbd

  13. #13
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    Hello
    I have good news , I believe that my no circulation coolant problem is solved , Today , I checked the valve's position and find out it was in the middle , not completely open or closed , so I opened and then I closed , started my BMW , let it run for more than 15 min. , check the control valve's inlet and outlet hoses and both were at ambient temperature (OK) , check the radiator hoses and both were warm (not very hot I can keep my hand on both) , check the cap and opened to vent air and it worked ok , the engine temperature was normal and engine was running very smooth .
    So , every body , THANKS for your help and good will
    Luis 320i

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