Mercedes-Benz 2009 CLK-Class Operator's Manual page 298

Practical hints
Vehicle status messages in the multifunction display
Display messages
Top Up Coolant
B
See Operator's
Man.
G Warning!
Do not spill antifreeze on hot engine parts. Antifreeze contains ethylene glycol which may burn if it comes into contact with hot engine parts.
You could be seriously burned.
! Do not ignore the low engine coolant level warning. Extended driving with the message and symbol displayed may cause serious engine
damage not covered by the Mercedes-Benz Limited Warranty.
Do not drive without sufficient amount of coolant in the cooling system. The engine will overheat causing major engine damage.
296
Possible cause/consequence
The coolant level is too low.
Possible solution
X
Add coolant ( Y page 232).
X
If you have to add coolant frequently, have the
cooling system checked at an authorized
Mercedes-Benz Center.