2008 MERCEDES-BENZ SL55AMG engine overheat

141 Controls in detail
Instrument cluster
Coolant temperature gaugeResetting trip odometer
Make sure you are viewing the trip
odometer display (
page 143).
If it is not displayed, press the
jork button on the multi-
function steering wheel repeatedly
until the trip odometer appears.
Press and hold reset button1
(
page 140) until the trip odometer is
reset.
Warning!G

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 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.
!Excessive coolant temperature triggers the
coolant temperature warning lamp (
page 348)
and a warning in the multifunction display
(
page 383).
The engine should not be operated with the cool-
ant temperature above 248°F (120°C). Doing so
may cause serious engine damage which is not
covered by the Mercedes-Benz Limited
Warranty.
iDuring severe operating conditions, e.g.
stop-and-go traffic, the coolant temperature may
rise close to 248°F (120°C).

268 Operation
Driving instructions
Power assistanceBrakes
Warning!G
The brake system requires electrical energy
for operation.
A malfunction in the vehicle’s power supply
or electrical system may impair brake sys-
tem operation and switch it into its emer-
gency operation mode. In such a case, the
red brake warning lamp (
page 345) and
warning messages (
page 359) in the in-
strument cluster come on while driving. To
brake, the driver must then apply signifi-
cantly greater brake pedal pressure and de-
press the pedal much further to obtain the
expected braking effect. If necessary, apply
full pressure to the brake pedal. Brakes are
only applied to the front wheels. Stopping
distance is increased! If there is a malfunc-
tion in the electro-hydraulic brake system,
we recommend that the vehicle be trans-
ported with all wheels off the ground using
flatbed or appropriate wheel lift/dolly equip-
ment.
A tow bar must be used if circumstances do
not permit the use of the recommended
towing methods and the vehicle requires
towing with all four wheels on the ground.
Towing the vehicle with all four wheels on
the ground is only permissible for distances
up to 30 miles (50 km) and at a speed not to
exceed 30 mph (50 km/h). For more infor-
mation, see “Towing the vehicle”
(
page 434).
With the engine not running, there is no
power assistance for the brake and steering
systems. In this case, it is important to keep
in mind that a considerably higher degree of
effort is necessary to brake and steer the
vehicle.
Warning!G
After driving in heavy rain for some time
without applying the brakes or through wa-
ter deep enough to wet brake components,
the first braking action may be somewhat
reduced and increased pedal pressure may
be necessary to obtain expected braking
effect. Maintain a safe distance from
vehicles in front.
Resting your foot on the brake pedal will
cause excessive and premature wear of the
brake pads.
It can also result in the brakes overheating
thereby significantly reducing their effec-
tiveness. It may not be possible to stop the
vehicle in sufficient time to avoid an
accident.

269 Operation
Driving instructions
To help prevent brake disk corrosion after
driving on wet road surfaces (particularly
salted roads), it is advisable to brake the
vehicle with considerable force prior to
parking. The heat generated serves to dry
the brakes.
If your brake system is normally only
subjected to moderate loads, you should
occasionally test the effectiveness of the
brakes by applying above-normal braking
pressure at higher speeds. This will also
enhance the grip of the brake pads.Refer to the description of the Brake Assist
System (BAS) (page 91).
Brake pad wear or a leak in the system may
be the reason for low brake fluid in the
reservoir.
The brake fluid level in the reservoir may
be too low or the electro-hydraulic brake
system may be malfunctioning if the brake
warning lamp in the instrument cluster
comes on and an acoustic warning sounds
although the parking brake is released
(
page 345).
Observe additional messages in the
multifunction display that may appear, see
(
page 377) through (page 382).
Have the brake system inspected immedi-
ately. Contact an authorized
Mercedes-Benz Center.All checks and service work on the brake
system should be carried out by qualified
technicians only. Contact an authorized
Mercedes-Benz Center.
Only install brake pads and brake fluid
recommended by Mercedes-Benz.
!Because the ESP® operates automatically,
the engine must be shut off (SmartKey in starter
switch position 0 or 1or KEYLESS-GO*
start/stop button in position 0 or 1) when the
parking brake is being tested on a brake test
dynamometer.
Active braking action through the ESP
® may
otherwise seriously damage the brake system.
Warning!G
Make sure not to endanger any other road
users when carrying out these braking
maneuvers.
Warning!G
If other than recommended brake pads are
installed, or other than recommended brake
fluid is used, the braking properties of the
vehicle can be degraded to an extent that
safe braking is substantially impaired. This
could result in an accident.
Be certain to read and observe the warning
notices on brake pad replacement
(
page 96).
!When driving down long and steep grades,
relieve the load on the brakes by shifting into a
lower gear to use the engine’s braking power.
This helps prevent overheating of the brakes and
reduces brake pad wear.

277 Operation
Driving instructions
Catalytic converter
Your Mercedes-Benz is equipped with
monolithic-type catalytic converters, an
important element in conjunction with
the oxygen sensors to achieve substantial
control of the pollutants in the exhaust
emissions. Keep your vehicle in proper
operating condition by following our
recommended maintenance instructions
as outlined in your Maintenance Booklet.Emission control
Certain systems of the engine serve to
keep the toxic components of the exhaust
gases within permissible limits required by
law.
These systems, of course, will function
properly only when maintained strictly
according to factory specifications. Any
adjustments on the engine should there-
fore be carried out only by qualified
Mercedes-Benz Center authorized techni-
cians. Engine adjustments should not be
altered in any way. Moreover, the specified
service jobs must be carried out regularly
according to Mercedes-Benz servicing
requirements. For details refer to the
Maintenance Booklet.
!To prevent damage to the catalytic convert-
ers, only use premium unleaded gasoline in this
vehicle.
Any noticeable irregularities in engine operation
should be repaired promptly. Otherwise, exces-
sive unburned fuel may reach the catalytic con-
verter causing it to overheat and potentially start
a fire.
Warning!G
As with any vehicle, do not idle, park or op-
erate this vehicle in areas where combusti-
ble materials such as grass, hay or leaves
can come into contact with the hot exhaust
system, as these materials could be ignited
and cause a vehicle fire.

278 Operation
Driving instructions
Coolant temperature
During severe operating conditions, e.g.
stop-and-go city traffic, the coolant
temperature may rise close to approxi-
mately 248°F (120°C).
The engine should not be operated
with the coolant temperature over
248°F (120°C). Doing so may cause
serious engine damage which is not
covered by the Mercedes-Benz Limited
Warranty.
Warning!G
Inhalation of exhaust gas is hazardous to
your health. All exhaust gas contains carbon
monoxide (CO), and inhaling it can cause un-
consciousness and possible death.
Do not run the engine in confined areas
(such as a garage) which are not properly
ventilated. If you think that exhaust gas
fumes are entering the vehicle while driving,
have the cause determined and corrected
immediately. If you must drive under these
conditions, drive only with at least one win-
dow fully open at all times.
Warning!G

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 and can occur just
by opening the engine hood. Stay away
from the engine if you see or hear steam
coming from it. Turn off the engine, get
out of the vehicle and do not stand near
the vehicle until the engine has cooled
down.

282 Operation
Engine compartment
Hood
Opening
1Hood release
Warning!G
Do not pull the release lever while the vehi-
cle is in motion. Otherwise the hood could
be forced open by passing air flow.
This could cause the hood to come loose
and injure you and/or others.
Warning!G
If you see flames or smoke coming from the
engine compartment, or if the coolant tem-
perature gauge indicates that the engine is
overheated, do not open the hood. Move
away from the vehicle and do not open the
hood until the engine has cooled. If neces-
sary, call the fire department.
Warning!G
You could be injured when the hood is open
– even when the engine is turned off.
Parts of the engine can become very hot. To
prevent burns, let the engine cool off com-
pletely before touching any components on
the vehicle. Comply with all relevant safety
precautions.
Warning!G
To help prevent personal injury, stay clear of
moving parts when the hood is open and the
engine is running.
The radiator fan may continue to run for ap-
proximately 30 seconds or may even restart
after the engine has been turned off. Stay
clear of fan blades.
Warning!G
The engine is equipped with a transistorized
ignition system. Because of the high voltage
it is dangerous to touch any components (ig-
nition coils, spark plug sockets, diagnostic
socket) of the ignition system

with the engine running

while starting the engine

if ignition is “on” and the engine is
turned manually

288 Operation
Engine compartment
Coolant
The engine coolant is a mixture of water
and anticorrosion/antifreeze.
When checking the coolant level,

the vehicle must be parked on level
ground

the coolant temperature must be be-
low 158°F (70°C)The coolant expansion tank is located on
the passenger side of the engine compart-
ment.
1Coolant expansion tank
Using a rag, slowly turn the cap approx-
imately one half turn counterclockwise
to release any excess pressure.
Continue turning the cap counterclock-
wise and remove it.
Warning!G
In order to avoid any potentially serious
burns:

Use extreme caution when opening the
hood if there are any signs of steam or
coolant leaking from the cooling system,
or if the coolant temperature gauge indi-
cates that the coolant is overheated.

Do not remove pressure cap on coolant
reservoir if coolant temperature is
above 158°F (70°C). Allow engine to
cool down before removing cap. The
coolant reservoir contains hot fluid and
is under pressure.

Using a rag, slowly open the cap approx-
imately 1/2 turn to relieve excess pres-
sure. If opened immediately, scalding
hot fluid and steam will be blown out un-
der pressure.

Do not spill antifreeze on hot engine
parts. Antifreeze contains ethylene gly-
col which may burn if it comes into con-
tact with hot engine parts.

348 Practical hints
What to do if …
ProblemPossible cause/consequenceSuggested solution
DThe red coolant warning lamp
comes on when the engine is
running.There is insufficient coolant in the reservoir.
If this warning lamp comes on frequently,
there is a leak in the cooling system.
If the coolant level is correct, the electric ra-
diator fan may be broken. Immediately add coolant to prevent
engine from overheating
(
page 288).
Have the cooling system checked.
If the coolant temperature is below
248°F (120°C), you can continue
driving to the nearest authorized
Mercedes-Benz Center.
Avoid high engine loads (e.g. driving
uphill) and stop-and-go driving.
DThe red coolant warning lamp
comes on when the engine is
running and you hear a warning
sound.The coolant temperature has exceeded
248°F (120°C).Stop in a safe location as soon as pos-
sible and allow the engine and coolant
to cool down.