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Thread: Coolant Temp Sensor

  1. #1
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    2002 530i E39 (1/02)

    Coolant Temp Sensor

    I'm hoping someone can help ... I am a "new" owner of an '02 530i E39 (prod. 01/02).

    Autozone scanned because my SES light came on and they said it's the coolant temp. sensor... but I can't find where the thing is. There are also two sensors - square with 2 connectors and round with 4 connectors.

    Most of the CTSs I've seen on other vehicles are located in the block somewhere - but I don't see one on the block. The guy at A/Z said it's by the oil filter - but there are two there - the first one is the oil sensor - I pulled it out and could see the oil on it. The other one is extremely difficult to reach, so I figured I would check here first but I can't find anything that identifies where the CTS is ...

    Thanks in advance.

  2. #2
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    98 540iA (Prd 11/97)

    Welcome to Bimmerforums

    Here you go.
    Quote Originally Posted by jase007 View Post
    It is number 3 circled in this pic and known as a dual temp sending unit. One signal goes to DME / ECU for engine management and the other to the dash gauge.



    When I first got my touring ... replaced all sensors I could (intake + exhaust CPS, crank sensor, lower radiator hose coolant temp, etc...) . Not this one. Can't reach it without taking intake manifold off. Tried ... but hands aren't small enough and no leverage. Bentley manual and others say IM has to come off.
    Last edited by jamesdc4; 12-29-2009 at 09:18 PM.

  3. #3
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    Quote Originally Posted by AlexMundae View Post
    I'm hoping someone can help ... I am a "new" owner of an '02 530i E39 (prod. 01/02).

    Autozone scanned because my SES light came on and they said it's the coolant temp. sensor... but I can't find where the thing is. There are also two sensors - square with 2 connectors and round with 4 connectors.
    .
    Not that I don't trust AutoZone, but what was the code?

    Keep in mind the description of the code is the SYMPTOM not the CAUSE.
    For example if the temp is too low, it could be caused by a bad thermostat or temp sensor.

  4. #4
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    I don't mean to step on your toes James but the temperature sensor that most commonly fails in this case would be item number 4. I checked the sales history and we have replaced 7 sensors through the shop and sold 4 over the front counter in the past month. It is in the lower rad hose about 2.5" away from the rad right under the expansion tank. The part number is 13-62-1-433-077.


  5. #5
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    Quote Originally Posted by KJet540 View Post
    I don't mean to step on your toes James but the temperature sensor that most commonly fails in this case would be item number 4. I checked the sales history and we have replaced 7 sensors through the shop and sold 4 over the front counter in the past month. It is in the lower rad hose about 2.5" away from the rad right under the expansion tank. The part number is 13-62-1-433-077.
    Until we have the actual code, we really don't know what the issue is.

    It could be the thermostat... Just curious how many of those have moved through your shop?

  6. #6
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    err
    Quote Originally Posted by jamesdc4 View Post
    Here you go.
    I replaced that sensor with out removing the intake,I used a mirror and small open end wenches.

  7. #7
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    2002 530i E39 (1/02)

    they didn't give me the actual code ...

    James - in looking at the engine, I can't even see the sensor shown in the diagram - even using mirror. If there is a sensor there, BMW must have held it in a jig and built the car around it - LOL.

    FWIW: the dash guage works fine, but since it got cooler (in AZ) I've noiticed that the air from the heating vents is not very warm ... not sure how this relates (sorry for not including that in the first place).

    Max - I think you're right - rather than trusting AutoZone (as another poster so eloquently put it - there's a reason those guys work THERE) I think I am going to run by one of the local independent BMW shops to at least diagnose what the real problem is.

    Thanks to everyone - I'll let you know what it turns out to be.

  8. #8
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    Quote Originally Posted by KJet540 View Post
    I don't mean to step on your toes James but the temperature sensor that most commonly fails in this case would be item number 4. I checked the sales history and we have replaced 7 sensors through the shop and sold 4 over the front counter in the past month. It is in the lower rad hose about 2.5" away from the rad right under the expansion tank. The part number is 13-62-1-433-077.

    You can step on my toes if you like, just let me put on my steel toe shoes first.
    I posted the following from the same thread I got that quote from. jase007 was stepping on my toes in that thread too.
    Quote Originally Posted by jamesdc4 View Post
    Thank you. I was about to post that, but I had to give my kids a bath and get them in bed.
    I was also going to suggest that the OP edit their car list to include the model and model year or prodution date.

    Also, I find it interesting that we haven't included the coolant temp sensor as a cooling system part that needs replacement when doing a complete overhaul.
    ______________________________

    Okay. I'm still confused. Realoem shows the M52's coolant temp sensor in the lower radiator hose (part #4 in the diagram below) and not on the side of the head.
    http://www.realoem.com/bmw/showparts.do?model=DM63&mospid=47585&btnr=11_2638& hg=11&fg=35&hl=10



    It shows a similar location for the 540 M62 (part #12), not on the WP.
    http://www.realoem.com/bmw/showparts.do?model=DN63&mospid=47588&btnr=11_2267& hg=11&fg=35&hl=36


    Same thing for the M54!
    http://www.realoem.com/bmw/showparts.do?model=DT63&mospid=47587&btnr=11_2638& hg=11&fg=35


    Anyone care to elaborate (Apologies if I'm being an airhead. It's been a long day)?
    Last edited by jamesdc4; 12-29-2009 at 10:31 PM.

  9. #9
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    Max is correct. You can't just take someone from Autozone literately. My guts feeling is you need a new thermostat for your car.

  10. #10
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    Quote Originally Posted by 16valex View Post
    Max is correct. You can't just take someone from Autozone literately. My guts feeling is you need a new thermostat for your car.
    The fault code reader frequently used by the Autozone guys is, I believe, not BMW specific but generic.

  11. #11
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    Quote Originally Posted by MaxVQ View Post
    It could be the thermostat... Just curious how many of those have moved through your shop?
    To give you an idea, this is how many we've sold in the past year.

    Jan: 20
    Feb: 5
    Mar: 17
    Apr: 12
    May: 4
    Jun: 7
    Jul: 6
    Aug: 7
    Sep: 3
    Oct: 9
    Nov: 12
    Dec: 18

  12. #12
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    1995 325iS
    Call me crazy, but it looks like BMW's don't like cold weather.

  13. #13
    Join Date
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    bend
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    07 330xi

    330XI coolant temp sensor

    Hi,

    I also had BMW& AZ check the SES code, BMW wants to replace the termostat but the gauge reads fine.
    AZ read me the code message (coolant temp below thermostat setting)

    I think the thermostat is working fine & controlling the temp, the coolant sensor that reads the temp is bad but I don't know which one is (item 4 on previous tread?)


    Thanks,

  14. #14
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    E39 99 528iT

    It could be the thermostat, the water inlet temp or outlet temp sensors or a problem with the engine ecu, but the electrically heated thermostat is a common problem.

    The thermostat is partially electrically controlled from the engine ecu and gets inputs from radiator inlet and outlet temps, engine load and speed, throttle opening etc.

    The error "coolant temp below thermostat setting" probably means that the engine ecu controlled temp setting is not being met as the actual water temp is lower than that which the engine ecu is asking for.

    The thermostat has an inbuilt heater as well as the usual wax/spring arrangement. The engine ecu controls the heater part to assist with the thermostat opening and closing. The M54 and M52TU engines can and do operate at up to approx 109Deg C (others say up to 113 Deg C) under light load conditions to reduce emissions.

    The temp gauge shows normal over a wide operating temperature range so just because its showing mid range/normal doesn't mean the thermostat is working correctly. The thermostat heater part may be faulty but the wax/spring part will still work to control the temp and this temp may still be within the normal range of the temp gauge but outside the temp the engine is aking for.


    Hope this helps.

    RonR
    99 528iT M52TU

  15. #15
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    07 330xi

    330XI coolant temp sensor

    Thanks Aussie528iT

    After posting my message, I took the car for 20 minutes of higher RPM/speed driving, after restarting the engine the SES light went off.

    My wife drives this car only about 5 miles each way so the engine does not get to operating temp often, but this light just came on recently.

    I understand that the ECU is looking at temp over time so something is has changed, I don't want to spend time/money changing the wrong thing.
    The SES lite has been off for 2 days now.

    Thanks again,

    Mo

  16. #16
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    Quote Originally Posted by KJet540 View Post
    I don't mean to step on your toes James but the temperature sensor that most commonly fails in this case would be item number 4. I checked the sales history and we have replaced 7 sensors through the shop and sold 4 over the front counter in the past month. It is in the lower rad hose about 2.5" away from the rad right under the expansion tank. The part number is 13-62-1-433-077.

    So there is one in the hose and another in the engine block. Please describe the function of each.

  17. #17
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    Quote Originally Posted by gtxragtop View Post
    So there is one in the hose and another in the engine block. Please describe the function of each.
    - The one in the lower radiator hose is the input for aux fan
    - The one in the engine block is a dual temp sensor. One channel displays engine cooling temperature on your temperature gauge. The other channel is the input to to air-gas mixture control.

  18. #18
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    bmw 2000 323i

    2000 e46 TEMP SENSOR

    Does anybody know what the RESISTANCE reading of a good TEMP SENSOR is.. what Ohm value? This is the TEMP SENSOR going to aux fan? How do I know its bad. AUX FAN doesnt come on.
    THANKS SCOTT

  19. #19
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    E39 99 528iT

    For an M54 or M52TU engine there are 2 more temp sensors as well as the one in the lower radiator hose.
    No 13 here. http://www.realoem.com/bmw/showparts...01&hg=11&fg=30

    No 3 here.
    http://www.realoem.com/bmw/showparts...69&hg=11&fg=15

    RonR

  20. #20
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    Quote Originally Posted by 16valex View Post
    - The one in the lower radiator hose is the input for aux fan
    - The one in the engine block is a dual temp sensor. One channel displays engine cooling temperature on your temperature gauge. The other channel is the input to to air-gas mixture control.
    That makes sense. Thanks!

  21. #21
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    Quote Originally Posted by scottysr View Post
    Does anybody know what the RESISTANCE reading of a good TEMP SENSOR is.. what Ohm value? This is the TEMP SENSOR going to aux fan? How do I know its bad. AUX FAN doesnt come on.
    THANKS SCOTT
    I am a strong proponent when it comes to proper diagnosis, measuring resistance (Ohm) to rule out bad temp sensors etc., I don't like to waste money on part I don't need.

    But...in your case, the main culprit is the temp sensor, which has a service life of about 8-10y/100K or so. A new temp sensor is about $22.

    For $22, install new sensor and move on with your life. Change the sensor only when coolant is cold. Apply a tiny smear of grease on the O-ring before install. Do a quick swap (get the new part ready) so you don't lose much coolant.
    Last edited by cnn; 06-27-2010 at 12:54 PM.

  22. #22
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    2001 BMW 530i 4dr sedan
    I believe we may have the same problem. The code for this description is P0128 and the description says (engine coolant temp is below normal).

  23. #23
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    Quote Originally Posted by cougarbaseball View Post
    I believe we may have the same problem. The code for this description is P0128 and the description says (engine coolant temp is below normal).
    I'm 99% sure you need a new thermostat.

  24. #24
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    I just got the "Engine Failsafe Prog" and I just replaced the blown fuse. Temp gauge is now working properly too. I'll order a new coolant temp sensor tomorrow. Thanx for the lead.

  25. #25
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    E39 523i;E46 316i
    Digging up the old thread.My temperature gauge is slightly below normal.Just replaced the themostat,but still the reading is the same.Could it be the temparature sensor which is located in the engine block?E39 M52 1996.

    One low quality picture.
    Last edited by 316driver; 10-08-2010 at 06:03 AM.
    E39 523i;E46 316i


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