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The last coolant temperature sensor thread *M30 swap inside*

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    The last coolant temperature sensor thread *M30 swap inside*

    Hey Folks.

    I have searched.
    I own Frank M's swap guide.
    I have even googled...I need concrete results with real world info and not guesses at this rate lol

    what I'm working with:
    1989 E30
    M30b35 engine
    M30b35 Ecu
    &
    M20b25 wire harness

    AFAIK, the onboard CLUSTER TEMP sensor (black) needs to be M20 specific....

    HOWEVER...the COOLANT TEMP SENSOR (blue) needs to match the engine/ECU

    so with that said, my coolant temp sensor is a Beru st028 sensor which I picked up brand new, and according to Beru will work on BOTH the M20 and M30 bosch motronic systems.

    From what I've read we need an M30 *specific* coolant temperature sensor, otherwise with the wrong sensor it'll just over fuel and think the car is in startup mode the whole time (which I believe is my issues as it's running rich...VERY rich)

    SO...with that said, can anyone clarify this?
    is there another coolant temperature sensor part number (bosch/VDO) to recommend?

    TIA
    Ryan
    Originally posted by flyboyx
    i have watched my dog lick himself off a few times

    #2
    My car is running a brown and blue temp sensor.


    Sent from my iPad using Tapatalk


    1989 325is l 1984 euro 320i l 1970 2002 Racecar
    1991 318i 4dr slick top


    Euro spec 320i/Alpina B6 3.5 project(the never ending saga)
    Vintage race car revival (2002 content)
    Mtech 2 turbo restoration
    Brilliantrot slick top "build"

    Comment


      #3
      right, however it's to my understanding that the blue sensor is what regulates fuel delivery upon cold startup.

      the blue sensor is the SAME sensor used on M20 AND M30 engines?

      because the info I'm getting is conflicting..where both are going to be blue, but both will hold different values between the M20 vs M30 hence different sensors....both blue tho.
      Originally posted by flyboyx
      i have watched my dog lick himself off a few times

      Comment


        #4
        Originally posted by Mr. Burns View Post
        right, however it's to my understanding that the blue sensor is what regulates fuel delivery upon cold startup.



        the blue sensor is the SAME sensor used on M20 AND M30 engines?



        because the info I'm getting is conflicting..where both are going to be blue, but both will hold different values between the M20 vs M30 hence different sensors....both blue tho.

        Where are you finding this? From my knowledge it was the brown one that controls idle and the blue one that send info to cluster and i think you can use and 1.3 motronic brown and blue coolant temp sensors. Like i said on my car that is 1.3 motronic i have a brown and a blue and my car is fine

        From my research you need these two sensors





        1989 325is l 1984 euro 320i l 1970 2002 Racecar
        1991 318i 4dr slick top


        Euro spec 320i/Alpina B6 3.5 project(the never ending saga)
        Vintage race car revival (2002 content)
        Mtech 2 turbo restoration
        Brilliantrot slick top "build"

        Comment


          #5
          I think I may of had my logic reversed on what the role of each sensor does

          from what I understood the brown sensor managed ONLY the gauge cluster temp.
          and the roll of the blue was controlling signal to the ECU to determine fuel delivery especially on cold startups.

          so going by that logic, and from what you're telling me basically reverse what I thought this may resolve my issue with running super rich. because as of right now, I'm still running the black M30b35 2 pin connector, and I have zero reading up on my dashboard.

          I'll pick up the proper brown sensor this evening...

          for clarity...the brown sensor will also send the info to the ECU for proper fuel mixture?

          I feel like I have a glimmer of hope starting here....
          Last edited by Mr. Burns; 06-17-2016, 03:27 PM.
          Originally posted by flyboyx
          i have watched my dog lick himself off a few times

          Comment


            #6
            Sorry to crush your glimmer of hope but... you're correct - the brown plug is the gauge / blue the DME.

            You run the M20 brown sensor (single pin vs. e34 two pin / black plug) to drive the e30 gauge, and the M30 blue sensor to drive the ECU.

            The blue plugs seem to be listed online as being the same for e30s, e28s and e34s, so if they're testing differently with an ohmmeter, then maybe one is damaged? I ran the M30 blue plug though on mine - I didn't ever try the blue M20 plug.

            Are you running an o2 sensor? Many e28 guys seem to think their cars run better with no O2 sensor, but I found with my M30 that the car ran rich and was much better with the o2 sensor once it had done some adapting.

            There's a comprehensive guide for testing your motronic system here:

            HPSI Motorsports is an industry leading manufacturer specializing high quality silicone hose kits for engine performance and longevity.
            Last edited by lukeADE335i; 06-18-2016, 05:26 AM.
            My e30: OEM+ with M30B35

            Comment


              #7
              Originally posted by lukeADE335i View Post
              Sorry to crush your glimmer of hope but... you're correct - the brown plug is the gauge / blue the DME.

              You run the M20 brown sensor (single pin vs. e34 two pin / black plug) to drive the e30 gauge, and the M30 blue sensor to drive the ECU.

              The blue plugs seem to be listed online as being the same for e30s, e28s and e34s, so if they're testing differently with an ohmmeter, then maybe one is damaged? I ran the M30 blue plug though on mine - I didn't ever try the blue M20 plug.

              Are you running an o2 sensor? Many e28 guys seem to think their cars run better with no O2 sensor, but I found with my M30 that the car ran rich and was much better with the o2 sensor once it had done some adapting.

              There's a comprehensive guide for testing your motronic system here:

              http://www.hiperformancestore.com/motronic.htm
              Agreed. the E30 gauge sender is a single-wire brown sensor, vs the e34 gauge sender which is a 2-wire black sensor. The blue senders, which go to the ECU, are the same for e30 m20b25 and e34 m30b35 motors.

              Comment


                #8
                This might be relevant to the thread but my temp gauge never *worked* since k swapped, I never had issues till I moved to Colorado...it hit around 101 in Denver and my upper hose blew...once that happened my gauge reached 3/4 and it has never risen before sooo...my thought is a faulty thermostat or a sensor? I'm using the stock sensors that came with the m30b35. I'm using a stock b35 harness.
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                Comment


                  #9
                  I had running rich issues when I finished my m30 build too, once I had the o2 sensor plugged in, the problem was solved.

                  Do you have the ecu sensor, and cluster sensor plugs wrong way around? does you temp gauge work correctly?
                  ///Monstrosity. (OO≡≡[][]≡≡OO)

                  Aside from showing yourself to be offensive, lacking experience and ignorant in the ways of business, you're also illiterate and imprudent. Beyond that, your sense of liability is severely impaired.

                  Comment

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