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Thread: e36 Coolant flow circuit

  1. #1
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    e36 Coolant flow circuit

    Hello everyone

    I will be making some tests on my coolant system and though it would be a good ideia to study the flow of coolant first

    The car in question is an 1992 EURO E36 320I with the m50b20tu engine


    I actually made a drawing i believe to be acurate and i would like to share it with anyone who might be interested
    im not sure how similar it is on other e36's

    While studying the system i came up with the questions related to the 'side circuit' of if.
    I am refering to the small. t.stat in the airbox and the coolant lines in the trhotle body

    My questions are:
    1- does coolant flow around/trhough the throttle body to prevent the butterfly valve freezing shut?
    Ans : yes exactly

    2- what does the t-stat ( the tiny one in the airbox) do?
    Ans: restricts coolant flow through the throtle body when air temp is warm

    3- how does the tiny t-stat work? seems pretty small and simple

    ps: i refer to the airbox t-stat as t-stat n2

    And sorry for the rough drawing im really no artist, just trying to visualize the whole thing
    Attached Images Attached Images
    Last edited by Tiago320; 06-03-2020 at 08:14 AM. Reason: Update

  2. #2
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    here is one from the M52 TU, maybe that helps, and from M42 http://www.m42club.com/forum/index.php?topic=19099.0
    Attached Images Attached Images
    Last edited by shogun; 06-02-2020 at 09:49 PM.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    The stat in the air box has nothing to do with the cooling system. It just measures air temp for the DME. The lines around the throttle body do keep it warm, my 98 m52b28 has them and it makes a good place to put a sender for my second temp gauge. I think I bypassed the throttle body one winter and had no problems.

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  4. #4
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    Quote Originally Posted by jmo69 View Post
    The stat in the air box has nothing to do with the cooling system. It just measures air temp for the DME. The lines around the throttle body do keep it warm, my 98 m52b28 has them and it makes a good place to put a sender for my second temp gauge. I think I bypassed the throttle body one winter and had no problems.

    Sent from my SM-G950U using Tapatalk
    The airbox thermostat is fed with coolant, so its defenetly in some way part of it
    Good to know the throtle body heathing it is not enterely needed in the winter, let alone in the summer, since its always warm around here i might install a 2nd coolant temp sender as well.

  5. #5
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    The airbox thermostat cuts off the coolant flow through the throttle when the air is warm. It doesnt do anything to the air temp..

    The coolant flow keeps the throttle warm to keep ice from building up on the butterfly during driving,.. Meaning the ice makes the throttle frozen open.

    The entire cooling portion that goes to the throttle body is viewed as a defect.. Its pointless and creates more problems. Especially the intake coolant switch. Those usually rupture at some point and spew coolant into the intake.

    - - - Updated - - -

    Forgot to mention, early models had the coolant flow cutoff switch in the airbox. They stopped installing them from factory after 94 I think.

  6. #6
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    Quote Originally Posted by spyderg0d View Post
    The airbox thermostat cuts off the coolant flow through the throttle when the air is warm. It doesnt do anything to the air temp..

    The coolant flow keeps the throttle warm to keep ice from building up on the butterfly during driving,.. Meaning the ice makes the throttle frozen open.

    The entire cooling portion that goes to the throttle body is viewed as a defect.. Its pointless and creates more problems. Especially the intake coolant switch. Those usually rupture at some point and spew coolant into the intake.

    - - - Updated - - -

    Forgot to mention, early models had the coolant flow cutoff switch in the airbox. They stopped installing them from factory after 94 I think.
    what exatly is this the intake coolant switch? could you post an image of it plz?

  7. #7
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    Quote Originally Posted by Tiago320 View Post
    The airbox thermostat is fed with coolant, so its defenetly in some way part of it
    Good to know the throtle body heathing it is not enterely needed in the winter, let alone in the summer, since its always warm around here i might install a 2nd coolant temp sender as well.
    I don't see a place for coolant lines on the Realoem.com diagram of the airbox or a stat.
    https://www.realoem.com/bmw/enUS/sho...diagId=13_1708

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  8. #8
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    I'm not sure the answer about the butterfly freezing shut is true.

    Butterfly throttle plates have been unregulated as to the temp that they operate at for more than a century. Heating the intake track, specifically the throttle body, is a relatively new thing in the automotive world. I think that heating the intake/throttle body is something that the smog people like. There is also the idea that it might save gas somehow, but it saves 100,000 gallons of gas per day spread over millions of cars so any given car has little affect. I honestly don't know enough about this, but it's absolutely true that we have been motoring about the planet since the inception of motoring about the planet without heating the intake. Having said that, it's entirely possible that we have been heating the intake with the same water that goes to the heater for the Life Support System, which has always been a bypass circuit of the main cooling system. With recent (the last 20 years or so) developments in smog/emissions controls, intake heaters could become thermostatically controlled, but whatever the reason, freezing butterfly plates is not it.

  9. #9
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    Not in that section, go to engine-cooling-hoses(select the picture with the integrated expansion tank on the side like the 318's)

    - - - Updated - - -

    I dont see any point apart from preventing ice tbh

    - - - Updated - - -

    Quote Originally Posted by jmo69 View Post
    I don't see a place for coolant lines on the Realoem.com diagram of the airbox or a stat.
    https://www.realoem.com/bmw/enUS/sho...diagId=13_1708

    Sent from my SM-G950U using Tapatalk
    Not in that section, go to engine-cooling-hoses(select the picture with the integrated expansion tank on the side like the 318's)

    - - - Updated - - -

    Quote Originally Posted by JDStrickland View Post
    I'm not sure the answer about the butterfly freezing shut is true.

    Butterfly throttle plates have been unregulated as to the temp that they operate at for more than a century. Heating the intake track, specifically the throttle body, is a relatively new thing in the automotive world. I think that heating the intake/throttle body is something that the smog people like. There is also the idea that it might save gas somehow, but it saves 100,000 gallons of gas per day spread over millions of cars so any given car has little affect. I honestly don't know enough about this, but it's absolutely true that we have been motoring about the planet since the inception of motoring about the planet without heating the intake. Having said that, it's entirely possible that we have been heating the intake with the same water that goes to the heater for the Life Support System, which has always been a bypass circuit of the main cooling system. With recent (the last 20 years or so) developments in smog/emissions controls, intake heaters could become thermostatically controlled, but whatever the reason, freezing butterfly plates is not it.
    dont see any point apart from preventing ice tbh

    - - - Updated - - -

    Tomorrow im going to test how diferent temperatures afect the intake thermostat

  10. #10
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    If i remember its like 27f that that thermoatat turna flow on.. So.. I hope you have a realllly big cooler. Lol

  11. #11
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    Quote Originally Posted by spyderg0d View Post
    If i remember its like 27f that that thermoatat turna flow on.. So.. I hope you have a realllly big cooler. Lol
    Starting to think about removing it then, its never colder than 0ºC over here

  12. #12
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    Quote Originally Posted by Tiago320 View Post
    Starting to think about removing it then, its never colder than 0ºC over here


    Why remove it? Just leave it alone unless it's leaking, then fix it.

  13. #13
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    Quote Originally Posted by JDStrickland View Post
    Why remove it? Just leave it alone unless it's leaking, then fix it.
    The natural balance of things took its tol on the thermostat and ir broke during a pressure test.

  14. #14
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    Quote Originally Posted by JDStrickland View Post
    I'm not sure the answer about the butterfly freezing shut is true.

    Butterfly throttle plates have been unregulated as to the temp that they operate at for more than a century. Heating the intake track, specifically the throttle body, is a relatively new thing in the automotive world. I think that heating the intake/throttle body is something that the smog people like. There is also the idea that it might save gas somehow, but it saves 100,000 gallons of gas per day spread over millions of cars so any given car has little affect. I honestly don't know enough about this, but it's absolutely true that we have been motoring about the planet since the inception of motoring about the planet without heating the intake. Having said that, it's entirely possible that we have been heating the intake with the same water that goes to the heater for the Life Support System, which has always been a bypass circuit of the main cooling system. With recent (the last 20 years or so) developments in smog/emissions controls, intake heaters could become thermostatically controlled, but whatever the reason, freezing butterfly plates is not it.
    The early M42s were recalled specifically to address potential throttle freezing issues by retrofitting a different heater plate. On those engines the intake manifold studs that secure the throttle body were scarcely long enough to accommodate the new, thicker heater plate. No relation to emissions at all.

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