Page 198 of 286

ProblemPossible causes/consequences andMSolutions
?
The red coolant
warning lamp is lit
while the engine
is running.The coolant temperature is too high.
XStop the vehicle as soon as possible, paying attention to road and
traffic conditions.
XConsult a qualified specialist workshop.
?The red coolant
warning lamp is lit
while the engine
is running.The coolant temperature is too high.
If the vehicle is stopped after being subjected to extreme loads, the
coolant warning lamp may come on when the ignition is switched on
or the engine is restarted. Such loads can be, for example, driving in
mountainous terrain or driving with a trailer.
XRun the engine for approximately 1 minute at idling speed.
XConsult a qualified specialist workshop if the display message con-
tinues to be shown.
7
|The yellow
reserve fuel warn-
ing lamp is on. At
the same time,
0
appears in the
fuel tank content
display while the
engine is running,
although there is
fuel in the fuel
tank.
The fuel filler cap is not closed.
XClose the fuel filler cap.
You will hear a click when the fuel filler cap is closed fully.
XIf the malfunction continues to be displayed, have it rectified imme-
diately at a qualified specialist workshop.
;
The yellow Check
Engine indicator
lamp is lit up or
flashes while the
engine is running.You have used up all fuel in the tank.
The engine is running in emergency mode.
XRefuel at the nearest gas station (Ypage 124).
XBleed the fuel system (Ypage 120).
XStart the engine three to four times in succession after refueling.
Emergency running mode will be canceled. The vehicle does not
need to be checked.
;The yellow Check
Engine indicator
lamp is lit up or
flashes while the
engine is running.The injection control is malfunctioning.
The engine is running in emergency mode.
Engine power output may be reduced.
XHave the vehicle checked at a qualified specialist workshop as soon
as possible.
In some states it is legally prescribed that after the Check Engine
indicator lamp lights up you must contact a qualified specialist work-
shop immediately. Observe the legal requirements.
196Indicator and warning lamps in the instrument cluster
On-board computer and displays
Page 218 of 286

Overview of the engine compartment
Example: engine
:
Coolant expansion tank cap (Ypage 218)
;DEF filler neck cap (Ypage 126)
=Engine oil filler neck cap (Ypage 216)
?Brake fluid expansion tank cap
(Ypage 219)
AWasher fluid reservoir cap (Ypage 220)
Regularly check the fluid level and the assembly
for leaks. If you detect fluid loss, e.g. oil flecks on
the vehicle parking space, consult a qualified
specialist workshop immediately.
Engine oil
General notes
!Engine oil gets dirty in the course of opera-
tion and its quality and volume are gradually
diminished. Regularly check the oil level, and
top up or have it replaced as needed.
Observe the information on engine oils and oil
consumption in the "Technical data" section
(
Ypage 277).
You can check the oil level in the engine:
Ron the display of the on-board computer
Rwith the oil dipstick
Checking the oil level shown in the dis-
play
If at extremely low temperatures no engine oil
level is displayed after 5 minutes, repeat the
engine oil level check after another 5 minutes.
If an oil level reading is still not displayed, check
the engine oil level with the dipstick
(
Ypage 217). Have the engine oil level checked
at a qualified specialist workshop. Only check the oil level when the engine is at
normal operating temperature.
XPark the vehicle on a level surface.
XSwitch off the engine.
XWait 5 minutes.
XTurn the key to position
2in the ignition lock.
The display is activated.
XVehicles without steering wheel buttons:
press the 4menu button on the instrument
cluster (
Ypage 33) repeatedly until the dis-
play shows the 1symbol.
The --:--
display message appears in the
display while the engine oil level measure-
ment is running.
XVehicles with steering wheel buttons:
press the Ëservice button on the instrument
cluster (
Ypage 33).
The 4 Engine oil level Measuring
inprogressdisplay message appears in the
display while the engine oil level measure-
ment is in progress.
Display message for vehicles without steer-
ing-wheel buttons: the display may show the
following messages after the engine oil level
measurement.
1Action
OKXDo not add oil.
– 1.0 qtsXAdd the amount of oil
shown (Ypage 218).
XCheck the engine oil level
again after a few minutes.– 1.5 qts
– 2.0 qts
HIThe oil level is too high.
XHave excess oil removed.
Measurement units in the display:
RqtsUSA only
RltrCanada only
Display message for vehicles with steering- wheel buttons: the display may show the fol-
lowing messages after the engine oil level meas-
urement.
1Action
Engineoillevel OKXDo not add oil.
216Engine compartment
Maintenance and care
Page 220 of 286

XInsert oil dipstick:back into the guide tube
as far as it will go and remove it again.
If the level is between minimum mark =and
maximum mark ;, the oil level is correct.
XIf the oil level has dropped to or below mini-
mum mark=, open cap ?and add engine oil
(
Ypage 218).
The difference in quantity between marks ;
and =is approximately 2 qt (2 l).
XInsert the oil dipstick into the guide tube as far
as it will go.
XClose the hood (Ypage 215).
OM651 4-cylinder diesel engine:
At outside temperatures between 32 ‡ (–0 †)
and 86 ‡ (30 †), the oil level can be checked
when the engine is cold.
Measuring the engine oil when the engine is cold
is less precise than measuring when the engine
is at normal operating temperature.
When the appropriate warning is shown in the
display
XAdd engine oil (Ypage 218)
or
XHave engine oil siphoned off.
Adding engine oil
GWARNING
If engine oil comes into contact with hot com- ponents in the engine compartment, it may
ignite. There is a risk of fire and injury.
Make sure that engine oil is not spilled next to
the filler neck. Let the engine cool down and
thoroughly clean the engine oil off the com-
ponents before starting the engine.
!The alternator is located below the engine
oil filler neck. If engine oil spills onto the alter-
nator, there is a danger of alternator damage.
Be very careful when adding engine oil.
HEnvironmental note
When adding oil, take care not to spill any. If
oil enters the soil or waterways, it is harmful to
the environment.
!Do not add too much oil. adding too much
engine oil can result in damage to the engine
or to the catalytic converter. Have excess
engine oil siphoned off.
!Do not use any additives in the engine oil.
This could damage the engine.
XOpen the hood (Ypage 214).
XUnscrew and remove cap ?.
XAdd engine oil.
XReplace cap?on the filler neck and tighten.
When doing so, make sure that the cap
engages correctly.
XCheck the oil level with the oil dipstick
(Ypage 217) or on the display (Ypage 216).
XClose the hood.
Coolant
GWARNING
The engine cooling system is pressurized, par-
ticularly 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 and/or fill the cool-
ant if the vehicle is on a level surface and the
engine has cooled down. The coolant tempera-
ture must be below 122 ‡ (50 †).
!Check the engine cooling and heating sys-
tem regularly for leaks.
If a large quantity of coolant is lost, have the
cause traced and rectified at a qualified spe-
cialist workshop.
GWARNING
If antifreeze comes into contact with hot com- ponents in the engine compartment, it may
ignite. There is a risk of fire and injury.
Let the engine cool down before you add anti-
freeze. Make sure that antifreeze is not spilled
next to the filler neck. Thoroughly clean the
antifreeze from components before starting
the engine.
!Take care not to spill any coolant on painted
surfaces. You could otherwise damage the
paintwork.
218Engine compartment
Maintenance and care