Coolant level sensor question
 

Fighting low coolant warning.
Bled, bled, re-bled, etc andthe red stick seems to be happy. Pops right up when I pull the cap (cold).

Tried 3 different sensors. Same effect. Is there any point in removing the rubber sheath from the sensor so it “feels” the magnet better?

Grasping at straws.

This thread, and that post in particular, has a lot of info (sort the good from the bad, as usual) on this topic.
https://xoutpost.com/bmw-sav-forums/...ml#post1111950

Is the expansion tank new? I recall reading in that thread and maybe elsewhere that some cheaper expansion tanks will skip on the magnet that is supposed to be in there. With no magnet in the expansion tank, the sensor will not work properly. The whole thing is very confusing until you read and understand post #16 there. I can see that the Chinese dept of reverse engineering missed out on that, and cut the corner to remove the magnet. And many of these cars don't even have a coolant level sensor, so they would not miss the missing magnet.

If it's the same old tank that was working fine before, then hopefully the explanation and photos in that thread will help with the debugging.

Thanks, read and re-read many of the explanations and think I have a pretty good grasp on it.

It is indeed an aftermarket and I suppose I will need to return it for a better quality one although this one gets good reviews. I will do the magnet and paper clip tests to see what that tells me.

Ok, so I pulled the sensor from the tank and held a magnet to the tip with the car running- no dash warning light. So, it’s either the internal magnet (or lack there of) or something else mechanical in the tank.

Yes, but even if these have a design defect like that (missing magnet), there are many cars out there without coolant level sensors who would not be affected, and might give great reviews.