Permanent Check Coolant Level message?
 

Hi guys – I have the Check Coolant Level (CCL) message and I can’t get rid of it. Background – replaced seam-split expansion tank and sensor. Topped off system with correct coolant. Bled system. Float is positioned correctly. I expected the CCL message to clear at this point, but it did not. I have driven the car for several weeks now under various temperature conditions and drive durations. I am 100% convinced the system is full and has no leaks. I have no dried residuals anywhere, no puddles, no drips, no white smoke, no odors, nothing. Temp gauge behavior normal. Wire harness to the sensor looks undamaged. I am stumped even after reading the forum search results. The only thing I have not tried is disconnecting the battery to see if it will clear the error message. Any thoughts on if that will work? Any other theories or ideas? Thanks in advance for your wisdom.

what about the low level sensor in the expansion tank ,did you check that? unless thats the sensor your talking about you checked.

You don't mention if you checked the coolant level sensor...which is not the "float" that you see when you undo the tank's lid (yes, it does fool many owners).

The sensor is screwed in from the bottom and is probably in a "dry" well (if like the expansion tanks since the m60-m62tu engines.

See #3 in the diagram below...and also check if the electrical harness (#6) is plugged in correctly to the sensor:

Yes, the sensor I was referring to - that I replaced - is the level sensor in the expansion tank (#3 in diagram). I assumed that was the one creating the message about the "level" of coolant. Is there another sensor somewhere that might generate the same message wording? Is there a "level" sensor in the radiator itself or elsewhere? Is this an error code that must be cleared manually? Thanks again.

Now I'm confused...is the red float bobbing up to the top of the expansion tank when you unscrew the lid (on a cold engine)?

Also, I edited (added) more info to my previous reply...go back and check that it all makes sense to you as to how the coolant level sensor & internal float communicate with each other. :)

You should see the internal float stick up like in the pic below (again, this is an e39 expansion tank...I've only been on the e53 forum for a year and don't know if there's a DIY for the e53's expansion tank). If the float is not rising to the top...then it has broken and the base of it (where the magnet resides) is down near the sensor...so the sensor would think that the tank is low on fluid...again, this is if the float is not rising to the top:

Thanks for the great detail on the system operation. Yes, the float bobs up correctly when the cap is opened. Since the float comes assembled with the expansion tank, I assume it was built properly with its magnets. Likewise, I bought the new electronic sensor from a reputable dealer so I think all of these expansion-tank related components are new and working. I even tried putting the old sensor back and it didn't change anything. I am back with the new sensor and the message persists. It's driving me crazy. The system seems to be operating fine, level steady at full for weeks, so driving the car is not a problem. But that message is always there and chimes in when you start the car and when you shut if off. It also leads to complacency and could mask a real leak if ignored, which I'm doing. Maybe there is a software bit stuck in memory somewhere. This is such a simple thing in cars - "detect low level of a fluid" - and yet BMW makes a Rube Goldberg system to do it. Ridiculous.

- Clear the codes / recycle and start the car
- rescan and do diagnostics
- Also, check with a multimeter (resistance and voltage) sensor(s) and related components

And there's still the possible battery nap. :) If you have NAV, make sure that the nav CPU goes to sleep 1st (power downs)...I would hate to put your Nav in peril over something simple:

http://bimmerboard.com/members/q/ori...%20Battery.jpg

pull the sensor from the dry well... see if the message is still there or if it is gone... if it is gone, the magnet inside fell down... if the message is still there, the problem is with sensor or down the line to the LCM.

with sensor out, put a magnet to the glass of the sensor (once you pull it out, you will see the clear glass i am talking about)... see if the contacts react... if contacts react, trace issue further in wiring...

Update – here’s the troubleshooting steps I did:

1. Pulled the sensor out of the well but still attached to the harness: message remained.

2. Condition #1 above, then put a magnet on the sensor: message went away.

3. Removed sensor from harness: message remained.

4. Inserted jumper wire into harness socket: message went away.

Based on this, somehow my system seems to be in a mode where it is operating backward. In other words, normally as the float dropped due to a coolant loss, the magnet would come down to the vicinity of the sensor; the switch would close and the message would appear.

I have the opposite – when a magnet is near, the switch closes and the system is happy – message goes away.

How on earth did the system get so jacked from just a simple tank and sensor replacement and why can’t I clear this message via some standard procedure?

Hopefully someone can shed some light, else I will just make the jumper wire permanent and avoid this headache. I check fluids often and I still have the temp gauge so I’m not too worried, but I hate to kludge things. Advice, comments very welcome! Thank you.

Sounds like it needs a recode - someone has done a swapsies

Magnet inside is misaligned?

Thanks for the continuing interest and replies. Bulk – can you please elaborate on what you mean by a “swapsie”?? As I mentioned, I replaced the tank and sensor with new, correct parts. How can just replacing these plug-and-play components affect or swap anything? Did I fail to do a procedure with the computer or something and the signal from the sensor lead wires got “swapped”? I’m a bit lost on what you are referring to. The reverse behavior I am seeing shouldn’t be caused by simply plugging in a new sensor, and there is only one way to plug it in.

Also, to do the “recode” – I assume you are referring to setting some flag somewhere – or “unswapping” whatever happened to begin with. Can you provide some detail? What is the parameter name and value and would I be using a GT1 or other software?

Terminator – you made me realize there is a test I could do; I could drain the expansion tank such that the float goes to the bottom and see if that makes the message go away. That would at least prove that there is indeed a magnet on the float and is working “properly” albeit backwards.

I just fixed this problem two weekends ago.

I did a complete coolant hose/waterpump job in December. And like many suggest, I also purchased a new Expansion tank.

From day one, I was getting this error. I checked the wiring over and over. I tried burping, and setting the water levels high and low, I changed the sensor twice.

Recently, I started leaking coolant out of the lower connector to the EX-Tank. I decided to get a new hose and another expansion tank. The leak went away and the low coolant level warnings did too. Bad tank.

Thanks for sharing your experience. So a "bad tank" really means that something is bad with the float system. I wonder if some of these aftermarket tanks are made without the magnet in the float? I mean a poor job of reverse engineering (instead of using a specification) would be to measure the tank dimensions and put a float in, but unless you really understood how the system worked, you would not embed a magnet in the float. Maybe that's it. The manufacturer would probably not get enough complaints to understand their tank was faulty since as we can see from the thread, figuring out why we get the message is not easily obvious. Just a theory...

permanent "check coolant level"message-how sensor works ?
 

Hi everyone,
It seems this is a long overdue explanation for how the coolant level sensor works on BMWs...
Everyone seems to agree the sensor is a reed relay that gets triggered by the magnet on the floater,the magnet on the floater causing the reed relay to close, right?!Only partially correct- But then, if the sensor is out of the dry-well or if the connector is disconnected, the "check coolant message" becomes permanent, also if the connector pins are shorted ( with a staple or something else), the message goes away!!! This seems to be "backward " !! So the explanation is simple:
The sensor should be "normal closed"- no check coolant message ! They achieve this, by having a SECOND magnet on the dry well !!!! This causes the reed relay( coolant level sensor) to close AS SOON inserted on the dry well! ( tested by me on an OEM tank). Now when the coolant level drops and the floater gets close to the reed relay, the magnetic field from the magnet on the floater will counter-effect the one on the dry well( sensor enclosure) to open up the relay= check coolant message !
This is how it works ! and this is why many after market expansion tank will throw this "check coolant level" message !- they don't have the second magnet on the dry well to keep the relay closed in normal operation !
OEM expansion tanks can fail also ( probably by this second magnet getting either loose or weak with the time- not being able to keep the relay closed in normal operation= coolant level OK, or by floater magnet falling on the bottom of the tank and counter effect the magnet keeping the sensor closed)
I hope this helps everyone understand once for all how this wicked system works!

If your sensor is reacting to the magnet ex situ, the tank is likely bad. Try another aftermarket tank, or fix it the first time and buy a genuine BMW tank from an online vendor.

Hi there, I know this tread is very old but how did you resolve the issue? Thanks..

Thanks for the excellent research and explanation. This seems to fill in all the mysteries in the rest of this thread. I'll try to remember it if I ever have any problems.

It just amuses me to see how many people don't know what or how a magnetic reed switch works. The Magnet operates the reed switch which is the coolant level sensor. It operates like a door alarm switch where you have a fixed magnet and a fixed switch. As the magnet gets into the proper proximity of the switch it either opens or closes the switch depending on if it's a NC or NO switch. Pretty easy circuit to understand. So it's not the magnet that is communication with the system but the magnet is operating the reed switch that then tells the system if the coolant is low or okay.

rswapp, what year and model is your e53?

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I don't think there is any doubt or misunderstanding by most people on here about any of that. Yes, reed switch, magnet, pretty straightforward. The mystery and unexplained behaviour comes when you consider the more intricate details as clearly and carefully laid out in post #16.

I've never had a problem with my coolant level sensor, but read this for interest in knowing how my car works, and solving problems. Tough when you know some things presented as facts are wrong, etc. But it really did seem weird ... until that post #16. After that, everything does make sense, and I feel I'll be able to carefully troubleshoot a problem if one ever occurs.

Have you done tests on your own system to confirm that post #16's system description it correct or not? I have not, but it does seem to be the explanation for all the (previously) confusing reports in just about every other post on this issue.

Me 2, post #16 should be made more obviuosly available to reference somehow. I was wanting to re-activate my low coolant warning system, just haven't done it yet. Post #16, assuming it is accurate is very good information.

I know this is an older post...

But did you ever resolve your mystery or dilemma?

PS great posts and images on this one 8-)

2006 BMW X5 E53 M54 3.0i

Turns out I don't have the low coolant light(bulb anyway) because I have the Low cluster. I think I might go down another path and add an an E30 expansion tank. There were too many problems with not only the sensor but the fact that the difference between overfilling the expansion tank and the low coolant level being triggered is only about a cup or two of coolant from what I can tell. Anyone with the high cluster, would that be about right?

Mine would trigger with only a cup low. You could still see coolant when you looked down the tank but definitely lets you know with plenty of warning.

E30 expansion tank?
 

Is the E30 Expansion an exact swap for E53? What do you mean by "Low Cluster" or "High Cluster"
(New to BMW here). Thanks

No, it's not a swap, I am going to add it in. There is a ton of info on both the expansion tank and the High and Low clusters in other threads if you want to get started on checking into those.

Basically for a High Cluster (not sure of the official name, but that's what is called in this forum), there is an LCD orange pixel display at the bottom of the instrument panel where it can show words like "COOLANT LEVEL LOW" or "TRANS FAILSAFE PROG.".

Low Cluster E53's do not have that display, so it can't tell you complex stuff like that, and makes up for some of it with more warning lights (e.g., as was recently confirmed in another thread, the low clusters have a coolant high temp warning light, and the high clusters do not - and probably make up for it with a gong sound and written warning).

Going beyond the display limitations, since the low cluster E53's do not have any way to indicate low coolant level, they do not have a coolant level sensor or the wiring to plug in a sensor. Even if a replacement coolant expansion tank comes with a coolant level sensor, there is no easy way to use it on a Low-Cluster E53.

New pics of the magnetic float from a genuine BMW expansion tank.

My expansion tank cracked along one of the vertical corners several months ago. Easy replacement.

It was a Genuine BMW, made in Germany by Modine in 2012, dealer installed by the PO in 2013, and failed catastrophically without warning 8 years and 38k miles later. Very lucky that it happened about two miles from my house and my son was in a position to immediately park and shut it down so quickly that only about a gallon of coolant was lost.

I finally cut it open yesterday to see what's in there. Pics follow, showing it to be a little different vs. the other earlier pics. Seems very well made. The magnet ring is clearly seen at the bottom of the float assembly. It is amazingly weak (low magnetic force).

Tests done at the time of replacement confirm that it works as described in post #16 above.

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@ oldscewel Can you make out where the second magnet is ? is it a ring much like the first one but around the bottom of the sensor hole?