Hi all,
I drive a 93, 525i, believe it's an E34 (125K miles). I changed my radiator a couple of weeks ago. But only recently, the sign "coolant level" pops up only a few seconds after I run then engine (it immediately goes off as I drive forward), and when I turn off the engine. The coolant level is stable. And the signs does not pop up while driving.
Is it simply because the sensor goes bad? If so, is it okay to buy aftermarket sensor, and where is the best place online?

I appreciate all of your insightful suggestions.

It could be the sensor, or maybe you didn't bleed out the system enough. If it's the sensor just get one from a dealer.

Yep, with the e36 325i, which has the same engine, the coolant sensor is a pretty common failure. It's an inexpensive part...just get a new one from the dealer and toss it in.

might want to check out your old one before ordering the new sensor, it might just need to be cleaned. sometimes gunk can cause it to stay open.

Thanks all.
Now there the sign "coolant level" doesn't appear period, and I didn't do anything yet. Does this means it is dead?

Thanks all.
Now there the sign "coolant level" doesn't appear period, and I didn't do anything yet. Does this means the sensor is dead?