Page 267 of 380
Problem Possible causes/consequences and
0050 Solutions00AC
The red coolant
warning lamp lights up
while the engine is
running and the coolant
temperature gauge is
at
the
start of the scale. The temperature sensor for the coolant temperature gauge is
defective.
The
coolant temperature
is no
longer being monitored. There is a
risk of engine damage if the coolant temperature is too high.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and
traffic conditions. Do not continue
driving under any circumstances.
X Secure the vehicle against rolling away ( Y page 160).
X Consult a qualified specialist workshop. Warning and indicator lamps in the instrument cluster
265
On-board computer and displays Z
Page 268 of 380

Problem Possible causes/consequences and
0050 Solutions00AC
The red coolant
warning lamp comes on
while the engine is
running.
The coolant level is too low.
If the coolant level is correct, the airflow to the engine radiator
may be blocked or the electric engine radiator fan may be
malfunctioning.
The coolant is too hot and the engine is no longer being cooled
sufficiently.
X
Observe the additional display messages in the multifunction
display.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 160).
X Wait until the engine has cooled down.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by snow, slush or ice.
X Check the coolant level and add coolant (Y page 302). Observe
the warning notes.
X If you need to add coolant more often than usual, have the
engine coolant system checked.
X At coolant temperatures below 248 ‡ (120 †) drive to the
nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in
mountainous terrain, and stop-and-go traffic. 00AC
The red coolant
warning lamp comes on
while the engine is
running.
A
warning tone
also sounds. The coolant temperature has exceeded 248 ‡ (120 †). The
airflow
to the
engine radiator
may be blocked or the coolant level
may be too low.
G WARNING
The engine is not being cooled sufficiently and may be damaged.
Do not drive when your
engine is overheated. This can cause some
fluids which may have leaked into the engine compartment to
catch fire.
Steam from the overheated engine can also cause serious burns
which can occur just by opening the hood.
There is a risk of injury.
X Observe the additional display messages in the multifunction
display.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 160).
X Wait until the engine has cooled down.266
Warning and indicator lamps in the instrument cluster
On-board computer and displays
Page 269 of 380

Problem Possible causes/consequences and
0050 SolutionsX
Make sure that the air supply to the engine radiator is not
blocked, e.g. by snow, slush or ice.
X Check the coolant level and add coolant (Y page 302). Observe
the warning notes.
X If you need to add coolant more often than usual, have the
engine coolant system checked.
X At coolant temperatures below 248 ‡ (120 †) drive to the
nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in
mountainous terrain, and stop-and-go traffic. Driving systems
Problem Possible causes/consequences and
0050 Solutions00BA
The red distance
warning lamp lights up
while the vehicle is in
motion.
G
WARNING
The distance to the vehicle in front is too small for the speed
selected.
There is a risk of an accident.
X Increase the distance. 00BA
The red distance
warning lamp lights up
while the vehicle is in
motion. A warning tone
also sounds. G
WARNING
You are approaching a vehicle or a stationary obstacle in your line
of travel at too high a speed.
There is a risk of an accident.
X Be prepared to brake immediately.
X Pay careful attention to the traffic situation. You may have to
brake or take evasive action.
More information about DISTRONIC PLUS (Y page 171) and
PRE-SAFE ®
Brake (Y page 69). Warning and indicator lamps in the instrument cluster
267On-board computer and displays Z
Page 304 of 380

Damage to the engine or exhaust system is
caused by the following:
R
using engine oils and oil
filters that have
not been specifically approved for the
service system
R replacing engine oil and oil filters after
the interval for replacement specified by
the service system has been exceeded
R using engine oil additives.
! Do not add too much oil. If the oil level is
above the "max" mark on the dipstick, too
much oil has been added. This can lead to
damage to the engine or the catalytic
converter. Have excess oil siphoned off. Example: engine oil cap
X
Turn cap 0043 counter-clockwise and remove
it.
X Add engine oil.
If the oil level is at or below the MIN mark
on the oil dipstick, add
1.1 US qt (1.0 liter)
of engine oil.
X Replace cap 0043 on the filler neck and turn
clockwise.
Ensure that the cap locks into place
securely.
X Check the oil level again with the oil
dipstick (Y page 301).
Further information on engine oil
(Y page 369). Checking and adding other service
products
Checking coolant level G
WARNING
The engine cooling system is pressurized,
particularly when the engine is warm. When
opening the cap, you could
be scalded by hot
coolant spraying out. There is a risk of injury.
Let the engine cool down before opening the
cap. Wear eye and hand protection when
opening the cap. Open the cap slowly half a
turn to allow pressure to escape.
Only check the coolant level when the vehicle
is on a level surface and the engine has cooled
down.
X Turn the SmartKey to position 2 in the
ignition lock (Y page 141).
On vehicles with KEYLESS-GO, press the
Start/Stop button twice (Y
page 141).
X Check the coolant temperature display in
the instrument cluster.
The coolant temperature must be below
158 ‡ (70 †). X
Slowly turn cap 0043 half a turn counter-
clockwise and allow excess pressure to
escape.
X Turn cap 0043 further
counter-clockwise and
remove it.
If the coolant is at the level of marker bar
0087 in the filler neck when cold, there is
enough coolant in coolant expansion
tank 0044
.302
Engine compartment
Maintenance and care
Page 373 of 380

Coolant
Important safety notes G
WARNING
If antifreeze comes into contact with hot
components in the engine compartment, it
may ignite. There is a risk of fire and injury.
Let the engine cool down before you add
antifreeze. Make sure that antifreeze is not
spilled next to the filler neck. Thoroughly
clean the antifreeze from components
before
starting the engine.
! Only add coolant that has been premixed
with the desired antifreeze protection. You
could otherwise damage the engine.
Further information on coolants can be
found in the Mercedes-Benz Specifications
for Service Products, MB Specifications for
Service Products 310.1, e.g. on the
Internet at
http://bevo.mercedes-benz.com. Or
contact a qualified specialist workshop.
! Always use a suitable coolant mixture,
even in countries where high temperatures
prevail.
Otherwise, the engine cooling system is not
sufficiently protected from corrosion and
overheating.
When handling coolant, observe the
important safety notes on service products
(Y page 365).
The coolant is a mixture of water and
antifreeze/corrosion inhibitor. It performs
the following tasks:
R corrosion protection
R antifreeze protection
R raising the boiling point
If the coolant has antifreeze protection down
to -35 ‡ (-37 †), the boiling point of the
coolant during operation is approximately
266 ‡ (130 †). The antifreeze/corrosion inhibitor
concentration in the engine cooling system
should:
R
be at least 50%. This
will protect the engine
cooling system against freezing down to
approximately -35 ‡ (-37 †).
R not exceed 55% (antifreeze protection
down to -49 ‡ [-45 †]). Otherwise, heat
will not be dissipated as effectively.
If the vehicle has lost coolant, add equal
amounts of water and antifreeze/corrosion
inhibitor.
Mercedes-Benz recommends an antifreeze/
corrosion inhibitor concentrate in
accordance with MB Specifications for
Service Products 310.1.
The coolant is checked with every
maintenance interval at a qualified specialist
workshop.
i When the vehicle is first delivered, it is
filled with a coolant mixture that ensures
adequate antifreeze and corrosion
protection.
Filling capacities Model Capacity
GLK 250 BlueTEC
approx. 10.6 US qt
(10.0 l) GLK 350
BlueEFFICIENCY
GLK 350 4MATIC
BlueEFFICIENCY
approx. 8.9 US qt
(8.4 l) i
Use MB 325.0 or MB 326.0 corrosion
inhibitor/antifreeze. Service products and filling capacities
371
Technical data Z