Engine MERCEDES-BENZ R-Class 2012 W251 Repair Manual

the vehicle, resulting in loss of consciousness
and even death.
To assure sufficient fresh air ventilation, open
a window slightly on the side of the vehicle
not facing the wind.
At the onset of winter, have your vehicle
winterproofed at a qualified specialist
workshop, e.g. at an authorized Mercedes-
Benz Center.
i Vehicles with a diesel engine: do not
cover the radiator, e.g. with a protective
cover. The measuring function of the
Onboard Diagnosis System may otherwise
provide inaccurate values. Some of these
values are required by law and must
therefore always be accurate.
Winter tires
At temperatures below 45 ‡(+7 †), use
winter tires or all-season tires. Both types of
tire are identified by the M+S marking.
Only winter tires bearing the i snowflake
symbol in addition to the M+S marking
provide the best possible grip in wintry road
conditions. Only these tires will allow driving
safety systems such as ABS and ESP ®
to
function optimally in winter, as these tires
have been designed specifically for driving on
snow.
Use M+S tires of the same make and tread on
all wheels to maintain safe handling
characteristics.
GWARNING
M+S tires with a tread depth of less than 1
/ 6
inch (4 mm) must be replaced immediately.
They are no longer suitable for use in winter.
Always observe the maximum permissible
speed specified for the M+S tires you have
mounted.
Once you have mounted the winter tires:XCheck the tire pressures ( Y page 329).XRestart the tire pressure monitor
( Y page 331).GWARNING
If you use your spare wheel when M+S tires
are mounted on the other wheels, be aware
that the difference in tire characteristics
impairs cornering ability and reduces driving
stability. Adapt your driving style accordingly.
Have the spare wheel replaced by a normal
wheel with an M+S tire at the nearest
Mercedes-Benz Center.
Snow chains
For safety reasons, Mercedes-Benz
recommends that you only use snow chains
which have been specially approved for your
vehicle by Mercedes-Benz, or are of a
corresponding standard of quality.
! Vehicles with the Adaptive Damping
System (ADS): do not drive in ADS SPORT
mode if snow chains have been mounted.
The vehicle may otherwise be damaged.
! There is not enough space for snow
chains on some wheel sizes. Observe the
information under "Tires and wheels" in the
"Technical Data" section to avoid damage
to the vehicle or the wheels.
R Only use snow chains when driving on
roads completely covered by snow. Do not
exceed the maximum permissible speed of
30 mph (50 km/h). Remove the snow
chains as soon as possible when you are no
longer driving on snow-covered roads.
R Local regulations may restrict the use of
snow chains. Applicable regulations must
be observed if you wish to mount snow
chains.
R Snow chains must not be mounted on
emergency spare wheels.
Driving tips169Driving and parkingZ

If you intend to mount snow chains, please
bear the following points in mind:
R you may not attach snow chains to all
wheel-tire combinations; see the
information under "Wheel and tire
combinations" in the "Wheels and tires"
section.
R mount snow chains only in pairs and only
to the rear wheels. Observe the
manufacturer's installation instructions.
! If snow chains are mounted on the front
wheels, the snow chains could grind
against the bodywork or components of the
chassis. This could result in damage to the
vehicle or the tires.
! Vehicles with steel wheels: if you wish
to install snow chains to steel wheels, make
sure that you remove the respective
wheels' hubcaps first. The hubcaps may
otherwise be damaged.
i You may wish to deactivate
ESP ®
(Y page 66) when pulling away with
snow chains mounted. This way you can
allow the wheels to spin in a controlled
manner, achieving an increased driving
force (cutting action).
Slippery road surfacesGWARNING
The outside temperature indicator is not
designed to serve as an ice-warning device
and is therefore unsuitable for that purpose.
Indicated temperatures just above the
freezing point do not guarantee that the road
surface is free of ice. The road may still be icy,
especially in wooded areas or on bridges.
GWARNING
On slippery road surfaces, never downshift in
order to obtain braking action. This could
result in drive wheel slip and reduced vehicle
control. Your vehicle's ABS will not prevent
this type of loss of control.
Drive particularly carefully on slippery road
surfaces. Avoid sudden acceleration, steering
and braking maneuvers. Do not use cruise
control.
If the vehicle threatens to skid or cannot be
stopped when moving at low speed:XShift the transmission to position N.
i
For more information on driving with
snow chains, see ( Y page 169).
GWARNING
Make sure that you do not endanger other
road users when you apply the brakes.
Driving systems
Cruise control
Important safety notes
Cruise control maintains a constant road
speed for you. It brakes automatically in order
to avoid exceeding the set speed. On long and
steep downhill gradients, especially if the
vehicle is laden or towing a trailer, you must
select shift range 1, 2 or 3 in good time. By
doing so, you will make use of the braking
effect of the engine, which relieves the load
on the brake system and prevents the brakes
from overheating and wearing too quickly.
Use cruise control only if road and traffic
conditions make it appropriate to maintain a
steady speed for a prolonged period. You can
set any road speed above 20 mph
(30 km/h).
GWARNING
The cruise control is a convenience system
designed to assist the driver during vehicle
operation. The driver is and must always
remain responsible for the vehicle's speed
and for safe brake operation.
Only use the cruise control if the road, traffic,
and weather conditions make it advisable to
travel at a constant speed.
170Driving systemsDriving and parking

Storing the current speed or calling up
the last stored speedGWARNING
The set speed stored in memory should only
be set again if prevailing road conditions and
legal speed limits permit. Possible
acceleration or deceleration differences
arising from returning to the preset speed
could cause an accident and/or serious injury
to you and others.
XBriefly pull the cruise control lever towards
you ?.XRemove your foot from the accelerator
pedal.
The first time cruise control is activated, it
stores the current speed or regulates the
speed of the vehicle to the previously
stored speed.
Setting a speed
GWARNING
Keep in mind that it may take a brief moment
until the vehicle has made the necessary
adjustments.
Increase or decrease the set vehicle speed to
a value that the prevailing road conditions and
legal speed limits permit. Otherwise, sudden
and unexpected acceleration or deceleration
of the vehicle could cause an accident and/
or serious injury to you and others.
XPress the cruise control lever to the
pressure point, up : for a higher speed or
down ; for a lower speed.XKeep the cruise control lever pressed until
the desired speed is reached.XRelease the cruise control lever.
The new speed is stored.
i Cruise control is not deactivated if you
depress the accelerator pedal. For
example, if you accelerate briefly to
overtake, cruise control adjusts the
vehicle's speed to the last speed stored
after you have finished overtaking.
Making adjustments in 1 mph (Canada:
1 km/h) incrementsXBriefly press the cruise control lever to the
pressure point, up : for a higher speed or
down ; for a lower speed.
The last speed stored is increased or
reduced.
Making adjustments in 5 mph (Canada:
10 km/h) increments
XBriefly press the cruise control lever
beyond the pressure point, up : for a
higher speed or down ; for a lower speed.
The last speed stored is increased or
reduced.
Deactivating cruise control
There are several ways to deactivate cruise
control:
XBriefly press the cruise control lever
forwards =.
or
XBrake.
Cruise control is automatically deactivated if:
R you depress the parking brake.
R you are driving below 20 mph (30 km/h).
R ESP ®
intervenes or you deactivate ESP ®
.
R you shift the transmission to position N
while driving.
If cruise control is deactivated, you will hear
a warning tone. You will see the Cruise
Control Off message in the multifunction
display for approximately five seconds.
i The last speed stored is cleared when you
switch off the engine.
172Driving systemsDriving and parking

DISTRONIC
Important safety notes
DISTRONIC regulates the speed and
automatically helps you maintain the
distance to the vehicle detected in front. It
brakes automatically in order to avoid
exceeding the set speed.
On long and steep downhill gradients,
especially if the vehicle is laden or towing a
trailer, you must select shift range 1, 2 or 3
in good time. By doing so, you will make use
of the braking effect of the engine, which
relieves the load on the brake system and
prevents the brakes from overheating and
wearing too quickly.
If a slower-moving vehicle is detected in front,
DISTRONIC causes your vehicle to brake and
maintain the preset distance to the vehicle in
front.
GWARNING
The Distronic requires familiarity with its
operational characteristics. We strongly
recommend that you review the following
information carefully before operating the
system.
GWARNING
When DISTRONIC brakes, the brake pedal is
pulled back (i.e. operated automatically). The
area around the pedal must not be blocked by
obstacles:
R do not place any objects in the footwell.
R ensure that floormats and carpets are fixed
securely. In particular, do not place several
floormats on top of one another.
R do not place your foot under the brake
pedal, as it could become trapped.
Non-compliance could lead you to cause an
accident in which you and/or others could be
seriously injured.
GWARNING
The Distronic is a convenience system. Its
speed adjustment reduction capability is
intended to make cruise control more
effective and usable when traffic speeds vary.
It is not however, intended to, nor does it,
replace the need for extreme care.
The responsibility for the vehicle's speed,
distance to the preceding vehicle and, most
importantly, brake operation to ensure a safe
stopping distance, always remains with the
driver.
The Distronic cannot take street and traffic
conditions into account. Complex driving
situations are not always fully recognized by
the Distronic. This could result in wrong or
missing distance warnings.
If there is no vehicle driving in front of you,
DISTRONIC functions like cruise control at a
speed range between 20 mph (30 km/h) and
120 mph (200 km/h). If a vehicle is driving in
front of you, it functions at a speed range
between 0 mph (0 km/h) and 120 mph
(200 km/h).
Do not use DISTRONIC while driving on roads
with steep gradients.GWARNING
DISTRONIC distance control is not a
substitute for the driver's active involvement.
It does not react to pedestrians or stationary
objects and cannot detect or predict the
road's course and the movements of the
vehicles in front.
DISTRONIC can only brake using 40% of the
vehicle's maximum possible braking force.
The driver must always pay attention to road,
weather and traffic conditions. He must steer,
brake and drive the vehicle so that he
maintains control over it.
High-frequency sources such as toll stations,
velocity measurement systems, etc. may
cause DISTRONIC to malfunction.
GWARNING
The Distronic cannot take road and traffic
conditions into account. Only use the
Distronic if the road, weather and traffic
Driving systems173Driving and parkingZ

Cruise control lever:To store the current speed or a higher
speed;To store the current speed or a lower
speed=To deactivate DISTRONIC?To store the current speed or to call up
the last stored speed
Switching on DISTRONIC, storing and
maintaining the current speed
GWARNING
The vehicle can be braked when DISTRONIC
is activated. For this reason, deactivate
DISTRONIC if the vehicle is to be set in motion
by other means (e.g. in a car wash or by
towing).
You can activate DISTRONIC in the following
circumstances:
R if the engine has been started and you have
been driving for up to two minutes
R while driving, except if you brake
R if the parking brake is not applied
R if ESP ®
is activated
R if the transmission is in position D
Activating while driving
When driving at speeds below 20 mph
(30 km/h) , you can only activate DISTRONIC
PLUS if the vehicle in front has been detected
and is shown in the multifunction display. If
the vehicle in front is not shown in the
multifunction display and is no longer being
detected, because it has changed lanes, for
example, DISTRONIC is deactivated and you
hear a warning tone.XBriefly pull the cruise control lever towards
you ? or press it up : or down ; to the
pressure point.
DISTRONIC is activated.XKeep the cruise control lever pressed
up : or down ; until the desired speed
is set.XRemove your foot from the accelerator
pedal.
Your vehicle adapts its speed to that of the
vehicle in front, but only up to the desired
stored speed.
i You can use the cruise control lever to set
the stored speed and the thumbwheel on
the cruise control lever to set the specified
minimum distance ( Y page 177).
i If you do not fully release the accelerator
pedal, the DISTRONIC Override message
appears in the multifunction display. The
set distance to a slower-moving vehicle in
front will then not be maintained. You will
be driving at the speed you determine by
the position of the accelerator pedal.
Driving
If there is no vehicle in front, DISTRONIC
operates in the same way as cruise control.
If a slower-moving vehicle is detected in front,
DISTRONIC causes your vehicle to brake and
maintain the preset distance to the vehicle in
front.
If DISTRONIC detects a faster-moving vehicle
in front, it increases the driving speed, but
only up to the desired speed you have stored.
GWARNING
If you depress the brake pedal, DISTRONIC is
deactivated. DISTRONIC will then no longer
brake your vehicle. In such cases, control the
distance from vehicles traveling in front with
the brake alone. You could otherwise cause
an accident and thereby injure yourself and
others. The driver remains fully responsible
Driving systems175Driving and parkingZ

GWARNING
DISTRONIC brakes your vehicle with a
maximum deceleration of 13 ft/s 2
(4 m/s 2
).
This corresponds to approximately 40% of
your vehicle's maximum possible braking
power.
You must apply the brakes yourself to avoid a
collision. DISTRONIC brakes the vehicle to
restore the set distance to the vehicle in front
or to restore the set speed. In this case, the
brake pedal is depressed automatically,
which can be seen by a movement of the
brake pedal.
Always keep the driver's footwell clear,
including the area under the brake pedal.
Objects in this area may impair pedal
movement and cause the DISTRONIC braking
function to malfunction.
Do not place your foot under the brake pedal
– your foot could become caught.
DISTRONIC displays in the
multifunction display
XPress the V or U button to select the
DISTRONIC menu (Y page 201).
Display when DISTRONIC is deactivated
When DISTRONIC is deactivated, you will see
the following in the multifunction display:
:Vehicle in front, if detected;Distance indicator, displaying current
distance to the vehicle in front=Specified minimum distance to the
vehicle in front, adjustable?Own vehicleDisplay when DISTRONIC is activated
After this time, you will see the following in
the multifunction display while DISTRONIC is
activated::DISTRONIC activated;Stored speed
When activating DISTRONIC and when setting
the speed, stored speed ; appears for
around five seconds.
After approximately five seconds, current
saved speed ; is displayed in the
multifunction display's status indicator
DTR XXX Miles .
Deactivating DISTRONIC
There are several ways to deactivate
DISTRONIC:
XBriefly press the cruise control lever
forwards :.
or
XBrake.
i
The last speed stored remains stored until
you switch off the engine.
i DISTRONIC is not deactivated if you
depress the accelerator pedal. If you
accelerate to overtake, DISTRONIC adjusts
178Driving systemsDriving and parking

ADS (Adaptive Damping System)
ADS is continuously electronically-controlled.
It adapts the damping characteristics to suit
the current operating conditions. The
damping is controlled for each wheel
individually. This improves driving safety and
tire comfort.
This depends on:
R your driving style
R the road surface conditions
R the ADS setting
R the vehicle level setting
Your selection remains stored even if you
remove the SmartKey from the ignition lock.
You can choose between the following ADS
settings:
R AUTO for normal driving situations;
indicator lamps ; and = are off.
R SPORT for sporty driving; indicator
lamp ; is on.
R COMF for a more comfortable ride;
indicator lamp = is on.
XStart the engine.XPress button : repeatedly until the
desired setting is selected.
Level control
Level control adapts the vehicle level
automatically to the current operating and
driving situation. This results in reduced fuel
consumption and improved handling.
Make changes to the vehicle level while the
vehicle is in motion. This enables the vehicle
to adjust to the new level as quickly as
possible.
The vehicle level may change visibly when you
park the vehicle and the outside temperature
changes. When the temperature drops, the
vehicle level is lower; with an increase in
temperature, the vehicle level rises.
When you unlock the vehicle or open a door,
the vehicle begins to balance the load
discrepancies while still parked. However, for
significant level changes, e.g. after the
vehicle has been stationary for a long period,
the engine must be on. For safety reasons,
the vehicle is only lowered when the doors are
closed. Lowering is interrupted if a door is
opened and continues once the door has
been closed.GWARNING
Make sure no one is near the wheel housing
or under the vehicle when you lower the
vehicle while it is standing still. Limbs could
become wedged into or under the vehicle.
For safety reasons, the vehicle can only be
lowered with all doors and the tailgate closed.
Lowering is interrupted if a door or the tailgate
is opened and will continue after the door is
closed again.
! When driving in very poor road conditions,
select a high vehicle level in good time.
Make sure that there is always sufficient
ground clearance to prevent damage to the
vehicle.
! Remove the key from the ignition lock
before raising the vehicle completely, e.g.
with a vehicle lift.
Basic settings
Select raised level for very poor road
conditions ( Y page 182) or highway level for
normal road conditions ( Y page 182).
Driving systems181Driving and parkingZ

The vehicle is automatically lowered to high-
speed level when you:
R drive faster than 70 mph (112 km/h)
R drive between 60 mph (96 km/h) and
70 mph (112 km/h) for approximately
20 seconds.
The individual vehicle levels differ from
highway level as follows:
R +1.97 in (+ 50 mm) at the raised level
R +/-0 in (+/-0 mm) at the highway level
R -0.47 in (-12 mm) at the high-speed level
i The high-speed level is not available if you
are pulling a trailer. Observe the notes on
driving with a trailer ( Y page 191).
i Observe the speed limitations. Drive
carefully at an appropriate speed.
Raised level
Only select raised level when this is
appropriate for the road conditions.
Otherwise, fuel consumption may increase
and handling may be affected.
If you select the raised level at a speed of over
40 mph (64 km/h) the Level Selection
Not Permitted message appears in the
multifunction display.XStart the engine.
Indicator lamp ; is not lit:
XPress button :.
Indicator lamp ; flashes. The vehicle rises
to raised level.While the adjustment is taking place, a
message appears in the multifunction
display, e.g.:
If you press the V, U , * or &
button on the multifunction steering wheel,
the message will disappear.
Once the vehicle has reached raised level,
indicator lamp ; remains lit. A message
appears in the multifunction display for
approximately five seconds, e.g.:
The level is automatically taken up to highway
level if you drive faster than 25 mph
(40 km/h).
Highway level
! Make sure that there is enough ground
clearance when the vehicle is being
lowered. It could otherwise hit the ground,
damaging the underbody.
XMake sure that the doors are closed.XStart the engine.182Driving systemsDriving and parking

! When parking, pay particular attention to
objects above or below the sensors, such
as flower pots or trailer drawbars.
PARKTRONIC does not detect such objects
when they are in the immediate vicinity of
the vehicle. You could damage the vehicle
or the objects.
The sensors may not detect snow and other
objects that absorb ultrasonic waves.
Ultrasonic sources such as an automatic
car wash, the compressed-air brakes on a
truck or a pneumatic drill could cause
PARKTRONIC to malfunction.
PARKTRONIC may not function correctly on
uneven terrain.
Minimum distanceCenterApproximately 8 in
(approximately 20 cm)CornersApproximately 6 in
(approximately 15 cm)
If there is an obstacle within this range, the
relevant warning displays light up and a
warning tone sounds. If the distance falls
below the minimum, the distance may no
longer be shown.
Warning displays
The warning displays show the distance
between the sensors and the obstacle. The
warning display for the front area is located
on the dashboard above the center air vents.
The warning display for the rear area is in the
roof lamp in the rear compartment.
Warning display for the front area
:Segments on the left-hand side of the
vehicle;Segments on the right-hand side of the
vehicle=Segments showing operational readiness
The warning display for each side of the
vehicle is divided into five yellow and two red
segments. PARKTRONIC is operational if
yellow segments showing operational
readiness = light up.
The selected transmission position
determines which warning display is active
when the engine is running.
Transmission
positionWarning displayDFront area activatedR or NRear and front areas
activatedPNo areas activated
One or more segments light up as the vehicle
approaches an obstacle, depending on the
vehicle's distance from the obstacle.
From the:
R sixth segment onwards, you will hear an
intermittent warning tone for
approximately two seconds.
R seventh segment onwards, you will hear a
warning tone for approximately two
seconds. This indicates that you have now
reached the minimum distance.
Driving systems185Driving and parkingZ

side. When you are passing another vehicle,
the warning is emitted only if the difference
in speed is less than 7 mph (12 km/h).
The yellow indicator lamp goes out if the
reverse gear is engaged. In this event, Blind
Spot Assist is no longer active.
The brightness of the indicator/warning
lamps is adjusted automatically according to
the ambient light.GWARNING
Blind Spot Assist is not active at speeds under
approximately 20 mph (30 km/h). The
indicator lamps in the exterior mirrors are
yellow. Vehicles in the monitoring range are
then not indicated.
Always pay attention to traffic conditions and
your surroundings. Otherwise, you may fail to
recognize dangers in time, cause an accident
and injure yourself and others.
Collision warning
If a vehicle is detected in the monitoring range
of Blind Spot Assist and you switch on the turn
signal, a double warning tone sounds. Red
warning lamp : flashes. If the turn signal
remains on, detected vehicles are indicated
by the flashing of red warning lamp :. There
are no further warning tones.
Switching on Blind Spot Assist
XMake sure that the radar sensor system
( Y page 208) and Blind Spot Assist
( Y page 210) are activated in the on-board
computer.XTurn the SmartKey to position 2 in the
ignition lock.
Warning lamps : light up red in the
exterior mirrors for approximately 1.5
seconds and then turn yellow.
Trailer towing
When you attach a trailer, make sure you have
correctly established the electrical
connection. This can be accomplished by
checking the trailer lighting. In this event,
Blind Spot Assist is deactivated. The indicator
lamp in the exterior mirrors lights up yellow
and the Blind Spot Assist Currently
Unavailable See Operator's Manual
message appears in the multifunction
display.
i You can deactivate the indicator lamps in
the exterior mirrors.
To do so, switch off Blind Spot Assist when:
R the SmartKey is in position 2 in the
ignition lock.
R the engine is not running.
R the electrical connection to the trailer
has been established.
Trailer towing
Notes on towing a trailer
Important safety notes
GWARNING
When towing a trailer, incorrect equipment
and driving style could cause you to lose
control of the vehicle.
Towing incorrectly or not observing this
Operator's Manual could lead to damage to
the vehicle and/or serious injuries. Observe
the following guidelines to ensure safe trailer
towing.
Contact a Mercedes-Benz Center if you need
further explanation of the information
contained in this Operator's Manual.
General information
R Only install an approved trailer coupling on
your vehicle.
Further information on availability and on
installation is available from any authorized
Mercedes-Benz Center.
R The bumpers of your vehicle are not
suitable for installing detachable trailer
couplings.
Trailer towing191Driving and parkingZ