Page 1 of 2 12 LastLast
Results 1 to 25 of 45

Thread: Coolant level sensor issue

  1. #1
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3

    Coolant level sensor issue

    Today, I flushed my system and also replaced my coolant tank. Bled everything and everything was fine until I got to work. Buddy tells me there is a large puddle underneath my car!

    Go out, sure enough, leaking from the coolant level sensor. It was loose! So, I tight it a bit by hand and get home. I figure maybe I need to take a wrench to it. As soon as I did, the plastic nut popped loose....odd? Remove the whole thing, maybe it was threaded wrong. Do it again....it is tight, take a wrench to it and it pops loose on the threads! It seems I can only get it so tight with my hand but if I try to apply a wrench, it does get tight again.

    So, remove the sensor, and screw on just the cap and it screws on tight! WTF!

    Get the old tank, same issue!

    So, should I try replacing the sensor or maybe use some pipe thread to try and get it tight?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  2. #2
    Join Date
    Aug 2013
    Location
    Seattle, WA
    Posts
    1,433
    My Cars
    1999 BMW M3 Coupe
    I replaced mine when I did my radiator. Probably best to just replace it than to worry about how long a tape job of some sort will last.
    1999 M3/2/5 - Titanium Silver - Track/Weekend Toy


  3. #3
    Join Date
    Dec 2013
    Location
    MA
    Posts
    125
    My Cars
    N/A
    Most likely there is a small crack somewhere on the plastic cap, preventing it from tightening, or the first few threads are just worn. When you remove the sensor it may screw down past the cracked portion so it still goes on tight. You may be able to find something in the hardware store with the same threads and re-use the sensor.

  4. #4
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    All good....bought another one. Hopefully, there will be no more issues. Does anyone use a wrench to tighten it or is it supposed to be hand tight?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  5. #5
    Join Date
    Oct 2003
    Location
    Seattle
    Posts
    5,776
    My Cars
    99 M3
    I believe hand tight should be good


    Sent from my iPhone using Tapatalk

  6. #6
    Join Date
    Aug 2013
    Location
    Seattle, WA
    Posts
    1,433
    My Cars
    1999 BMW M3 Coupe
    It's a plastic part so hand tight is fine. You don't want to torque anything plastic very much or it will break.
    1999 M3/2/5 - Titanium Silver - Track/Weekend Toy


  7. #7
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    While I agree that hand tight should be sufficient, the fact that a wrench, after being hand tight, could cause the nut to pop loose onto the thread with not even a quarter turn, leads me to believe there is an actual issue. Also, the fact that after my drive, the nut was loose worries me that hand tight might not be sufficient. Or, in my case, maybe I need a new sensor/seal. I'll be sure to update this thread when I get the new part.
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  8. #8
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    So I got the new sensor and I am just afraid to really crank on it. I got it as hand tight as possible and go from there. If that doesnt work, I will buy an OEM BMW tank and just suck it up. Any thought to using blue loctite maybe? Will that work on plastics?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  9. #9
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    Use thread seal tape, aka PTFE tape or plumber's tape. The tape also works as a deformable filler and thread lubricant. Typically the tape is wrapped around a pipe's thread three times before it is screwed into place. It is commonly used in applications including pressurized water systems, central heating systems, and air compression equipment, so it will work also for your problem.
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
    Join Date
    Oct 2003
    Location
    Seattle
    Posts
    5,776
    My Cars
    99 M3

    Coolant level sensor issue

    Quote Originally Posted by shogun View Post
    Use thread seal tape, aka PTFE tape or plumber's tape. The tape also works as a deformable filler and thread lubricant. It is commonly used in applications including pressurized water systems, central heating systems, and air compression equipment, so it will work also for your problem.
    The seal is not at the threads, which is the purpose of plumber tape. The threaded nut is for retention only, as there should be a rubber washer that seals the sensor to the tank which should have a brass/bronze insert at this joint. What brand of tank do you have?


    Sent from my iPhone using Tapatalk
    Last edited by bluptgm3; 08-02-2017 at 09:03 AM.

  11. #11
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    The tank is a febi/bilstein. The new sensor is febi. The old tank was a hella/behr. The old sensor was hella/behr. First, I tried to move the behr sensor over to the febi tank.....didn't get tight enough or would loosen as soon as it was hand tight and I applied the wrench. I tested the behr sensor back on the behr tank and the same thing happened, which surprised me. Both tanks have the brass insert at the joint, but the problem is I'm worried that the vibration will back the threaded nut off, which it did the other day and why I bought a new sensor. I have it hand tight as much as possible or should I say, I installed it with the tank in the car so I got it as tight as my fingers will allow. I'll continue to monitor it and see if it loosens over time.

    And I don't think he is saying the tape is to seal the sensor. The purpose of the tape is to provide enough friction from the retaining cap from unscrewing.
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  12. #12
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    Quote Originally Posted by BMWManiac View Post
    The tank is a febi/bilstein. The new sensor is febi. The old tank was a hella/behr. The old sensor was hella/behr. First, I tried to move the behr sensor over to the febi tank.....didn't get tight enough or would loosen as soon as it was hand tight and I applied the wrench. I tested the behr sensor back on the behr tank and the same thing happened, which surprised me. Both tanks have the brass insert at the joint, but the problem is I'm worried that the vibration will back the threaded nut off, which it did the other day and why I bought a new sensor. I have it hand tight as much as possible or should I say, I installed it with the tank in the car so I got it as tight as my fingers will allow. I'll continue to monitor it and see if it loosens over time.

    And I don't think he is saying the tape is to seal the sensor. The purpose of the tape is to provide enough friction from the retaining cap from unscrewing.
    That's not how PTFE tape works, or how it should be used. It's made to act as a gasket between the tiny spaces between mating threads. In the expansion tank's case, what seals is the rubber O-Ring at the base of the sensor. The threads are simply for engagement and the O-ring provides the pressure needed to hold the threads in place.

    When I refreshed my system I used a new O-Ring and tightened the sensor nut no more than 1/8 to 1/4 of a turn max. Hasn't loosened since. No PTFE tape and no leaks.

  13. #13
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    Quote Originally Posted by LockDots View Post
    That's not how PTFE tape works, or how it should be used. It's made to act as a gasket between the tiny spaces between mating threads. In the expansion tank's case, what seals is the rubber O-Ring at the base of the sensor. The threads are simply for engagement and the O-ring provides the pressure needed to hold the threads in place.

    When I refreshed my system I used a new O-Ring and tightened the sensor nut no more than 1/8 to 1/4 of a turn max. Hasn't loosened since. No PTFE tape and no leaks.
    The sensor comes with a new o-ring. I get it that the o-ring is what makes the seal. However, you can't keep the seal without the locking ring. If the locking ring loosens due to vibrations, then the seal will break. It happened to me. The nut loosened, and I saw the coolant leak out. I don't know if we're debating in circles here, but the bottom line is, without the locking ring staying lock, the seal will break.
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  14. #14
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    Quote Originally Posted by BMWManiac View Post
    The sensor comes with a new o-ring. I get it that the o-ring is what makes the seal. However, you can't keep the seal without the locking ring. If the locking ring loosens due to vibrations, then the seal will break. It happened to me. The nut loosened, and I saw the coolant leak out. I don't know if we're debating in circles here, but the bottom line is, without the locking ring staying lock, the seal will break.
    You're correct. The locking ring (nut?) shouldn't come off from vibrations. If you can hand tighten yours to the point where it spins off, then it'll most likely come loose on its own. More than likely there a hairline crack in the expansion tank or the nut.

  15. #15
    Join Date
    Oct 2003
    Location
    Seattle
    Posts
    5,776
    My Cars
    99 M3
    Quote Originally Posted by LockDots View Post
    More than likely there a hairline crack in the expansion tank or the nut.
    Unlikely the tank was split as most name brand tanks and replacements have a brass/bronze insert.


    Sent from my iPhone using Tapatalk

  16. #16
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    Quote Originally Posted by bluptgm3 View Post
    Unlikely the tank was split as most name brand tanks and replacements have a brass/bronze insert.


    Sent from my iPhone using Tapatalk
    Correct. Hence the "or the nut" comment.

  17. #17
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    Well, it seems to be holding just fine....now I am having the stupid issue #2 where the tank is full, but I keep getting the "Low coolant level." I'm wondering if the plug is installed incorrectly, but I'm pretty sure it is. What are the chances that the brand new sensor is faulty and DOR?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  18. #18
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    Quote Originally Posted by BMWManiac View Post
    Well, it seems to be holding just fine....now I am having the stupid issue #2 where the tank is full, but I keep getting the "Low coolant level." I'm wondering if the plug is installed incorrectly, but I'm pretty sure it is. What are the chances that the brand new sensor is faulty and DOR?
    It'll work even if it's backwards. It's simply a Reed switch (continuity through a magnetically latched switch). Take a meter to the two contacts on the sensor and measure continuity or reaiatance/impedance. It should read a dead short in one position and an open in the other. I forget which is which.

    That being said, if you don't get the message when you start the car but you do after driving, it means you either have air in the system or the coolant went low enough to trip the sensor mid drive, which typically means a leak or air.

  19. #19
    Join Date
    Oct 2003
    Location
    Seattle
    Posts
    5,776
    My Cars
    99 M3
    Quote Originally Posted by LockDots View Post
    That being said, if you don't get the message when you start the car but you do after driving, it means you either have air in the system or the coolant went low enough to trip the sensor mid drive, which typically means a leak or air.
    Yes if you lost coolant, generally it takes a couple of drive cycles to bleed out all of the air. And potentially a couple more once you start using the heater in the fall.



    Sent from my iPhone using Tapatalk

  20. #20
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    I'll keep bleeding/running the heater on full blast when I can and see if it improves. The warning comes on as soon as I start the car and shows again when I shut it off. After initial start and I acknowledge the fault, the error never pops up again during the drive....only at start and shut off.
    Last edited by BMWManiac; 08-07-2017 at 06:48 AM.
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  21. #21
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    Quote Originally Posted by BMWManiac View Post
    I'll keep bleeding/running the heater on full blast when I can and see if it improves. The warning comes on as soon as I start the car and shows again when I shut it off. After initial start and I acknowledge the fault, the error never pops up again during the drive....only at start and shut off.
    That changes the story a little. If you're getting it when you turn the key to "on" then it's detecting an open-circuit condition, meaning it thinks the coolant is low. Inspect and test your sensor.

    If I remember correctly you won't get a low-coolant warning while the engine is running. Only during Ignition-On and after Ignition-Off.

  22. #22
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    I have read before, but maybe this is speculation, that if there isnt enough coolant and maybe too much distilled water, the float wont rise or is that just complete nonsense?

    Testing isnt my forte but I do have an voltmeter....I will google how to test it and see if anyone knows what values I am looking for.
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  23. #23
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    So, at this point, I have no leaks, been driving it for a couple of days and I still get the low coolant message on start and shutoff.

    The strange thing I notice is, after starting the car, the low coolant level message appears, but will go away without me ever hitting the "check" button on the OBC....is that normal?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

  24. #24
    Join Date
    Feb 2009
    Location
    Long Island, NY
    Posts
    8,167
    My Cars
    97 M3 & 13 Rav4
    I haven't had that message in years but If memory serves me well (and it often doesn't) it's normal for it to go away on it's own.

    The fact that you have the message as soon as you turn the car on means the car "thinks" it's low on coolant. If you check your car in the morning (once it's had a chance to cool overnight) before you even crank it and you can see that you have coolant at or above the Cold/Kalt line and it doesn't go below the minimum while the engine is warming up or during use then it's really only left to three things. The sensor (doubt it at this point), the wiring (possible short telling the OBC it's always low on coolant), or the OBC itself (doubtful but possible because it's a simple "test" it does to determine if coolant is low).

  25. #25
    Join Date
    Feb 2002
    Location
    Orlando, FL
    Posts
    8,884
    My Cars
    Turbo 97 E36 M3, 99 M3
    i check it every morning and it is still above the sensor. I have seen it a little lower than the line, but as soon as I remove the cap, it flows back up to the line....maybe I need to keep adding coolant?
    Here is my plan. Remove wiring harness and attach it to the old sensor outside of the reservoir, upside down and see if the message is triggered....will that work? Old sensor didnt give me a warning. Now, I have read, but not confirmed, that these aftermarket tanks could be the cause of the problem? Is there another magnet on the opposite side of the tank that interacts with the magnet in the coolant sensor?
    1997 Arctic Silver/Black M3
    CES Stage IV (651rwhp/615rwtq @ 24 psi)

    1999 Techno Violet/Dove M3
    Auto/Convertible and staying stock!

Page 1 of 2 12 LastLast

Similar Threads

  1. WTB: coolant level sensor / brake light circuit
    By neiche in forum BMW Parts Wanted
    Replies: 0
    Last Post: 07-23-2003, 02:45 PM
  2. Coolant Level Sensor $$?
    By CJ in forum 1992 - 1999 M3 (E36)
    Replies: 11
    Last Post: 06-11-2003, 04:40 PM
  3. How do I Change the Coolant level sensor.
    By Sonic A in forum General BMW Mechanical Help sponsored by RM European Auto Parts
    Replies: 3
    Last Post: 04-29-2003, 08:54 PM
  4. A/C belt replacement and Coolant Level sensor Replacement
    By buckwilly in forum 1992 - 1999 M3 (E36)
    Replies: 11
    Last Post: 04-09-2003, 10:46 AM
  5. Anyone replace the coolant level sensor?
    By Jim O. in forum 1992 - 1999 M3 (E36)
    Replies: 7
    Last Post: 10-05-2001, 01:57 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •