Permanent Check Coolant Level message?

[EODguy]

rswapp, what year and model is your e53?

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[oldskewel]

Originally Posted by rswapp

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.

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.

[80stech]

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.

[Bermslayer]

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

[80stech]

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?

[Overboost]

Originally Posted by 80stech

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.

[Bermslayer]

Originally Posted by 80stech

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?

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

[80stech]

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.

[oldskewel]

Originally Posted by Bermslayer

...What do you mean by "Low Cluster" or "High Cluster"
(New to BMW here). Thanks

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.

[oldskewel]

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.