Mercedes-Benz 2009 M-Class Operator's Manual page 326

Practical hints
Vehicle status messages in the multifunction display
Display messages
Coolant
Ì
Stop car, switch
engine off.
G Warning!
Driving when your engine is overheated can cause some fluids which may have leaked into the engine compartment to catch fire. You could
be seriously burned.
Steam from an overheated engine can cause serious burns which can occur just by opening the engine hood. Stay away from the engine if
you see or hear steam coming from it.
Stop the vehicle in a safe location away from other traffic. Turn off the engine, get out of the vehicle and do not stand near the vehicle until
the engine has cooled down.
324
Possible cause/consequence
The coolant is too hot.
Possible solution
X
Stop the vehicle immediately as soon as it is
safe to do so.
X
Turn off the engine immediately.
X
Engage the parking brake.
X
Only start the engine again after the message
disappears. You could otherwise damage the
engine.
X
Observe the coolant temperature in the
multifunction display.
X
If the temperature rises again: Contact an
authorized Mercedes-Benz Center
immediately.
During severe operation conditions and stop-
and-go city traffic, the coolant temperature may
rise close to 248‡ (120†).