W211 E320 Message for Top-Up Coolant

[talithaxujl]

As a result of all the wonderful road trips I've taken in my 2008 W211 E320 CDI Sports, the mileage has reached 150K. On startup, it says to check and add coolant, but I already have it at its maximum level. My gut tells me it's the level switch, but I can't shake the feeling that I used the wrong coolant. I used prestone coolant, which claims to be compatible with all brands and types of coolant and can be used on any vehicle. I need your help deciding whether to flush and refill the coolant after replacing the sensor.

[blaisecj]

The washer's bottle is full, right?

[crispin_couturierz]

Typically, the coolant level sensor is integrated into the coolant expansion tank. To ensure its functionality, simply remove the plug and place a meter on top