Page 302 of 473
301 Operation
Engine compartment
The coolant expansion tank is located on
the passenger side of the engine compart-
ment.
SLK 350 (example illustration)
1Coolant expansion tank
2Cap
3Marking bar in the expansion tank
Using a rag, turn cap2 slowly approx-
imately one half turn counterclockwise
to release any excess pressure.
Continue turning cap2 counterclock-
wise and remove it.
The coolant level is correct if the level
for cold coolant: reaches marking
bar3 in expansion tank1
for warm coolant: is approximately
0.6 in (1.5 cm) higher
Add coolant as required.
Replace and tighten cap2.
For more information on coolant, see
“Coolants” (
page 448).
Using a rag, slowly open the cap approx-
imately 1/2turn 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
glycol which may burn if it comes into
contact with hot engine parts.
Page 371 of 473

370 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
•The cooling fan for the coolant is
malfunctioning.Observe the coolant temperature display
(
page 127).
If the coolant temperature is below 120°C,
you may continue driving to the nearest
specialist workshop.
Avoid heavy loads on the engine (e.g. by
driving uphill) as well as stop-and-go traffic.
Have the fan replaced as soon as possible.
/Top up coolant
See Oper. ManualThe coolant level is too low.Add coolant (page 300).
Comply with all warnings while doing so.
If you have to add coolant frequently,
have the cooling system checked by an au-
thorized Mercedes-Benz Center.
Warning!G
Do not spill antifreeze on hot engine parts.
Antifreeze contains ethylene glycol which
may burn if it comes into contact with hot
engine parts. You could be seriously burned.
!Do not ignore the low engine coolant level
warning. Extended driving with this message and
symbol displayed may cause serious engine
damage not covered by the Mercedes-Benz
Limited Warranty. Do not drive without sufficient
amount of coolant in the cooling system. The
engine will overheat, causing major engine
damage.
Page 449 of 473

448 Technical data
Fuels, coolants, lubricants, etc.
Coolants
The engine coolant is a mixture of water
and anticorrosion/antifreeze, which pro-
vides:
Corrosion protection
Freeze protection
Boiling protection (by increasing the
boiling point)
The cooling system was filled at the factory
with a coolant providing freeze protection
to approximately -35°F (-37°C) and corro-
sion protection.
If the antifreeze mixture is effective to
-35°F (-37°C), the boiling point of the cool-
ant in the pressurized cooling system is
reached at approximately 266°F (130°C).The coolant solution must be used year
round to provide the necessary corrosion
protection and increase boil-over protec-
tion. Refer to Maintenance Booklet for
replacement interval.
Coolant system design and coolant used
determine the replacement interval. The
replacement interval published in the
Maintenance Booklet is only applicable if
MB 325.0 Anticorrosion/Antifreeze solu-
tion or other Mercedes-Benz approved
products of equal specification are used to
renew the coolant concentration or bring it
back up to the proper level.
For information on other Mercedes-Benz
approved products of equal specification,
refer to the Factory Approved Service
Products pamphlet (USA only) or contact
an authorized Mercedes-Benz Center.To provide important corrosion protection,
the solution must be at least
50% anticorrosion/antifreeze (equivalent
to freeze protection to approximately
-35°F [-37°C]). If you use a solution that is
more than 55% anticorrosion/antifreeze
(freeze protection to approximately
-49°F [-45°C]), the engine temperature
will increase due to the lower heat transfer
capability of the solution. Therefore, do not
use more than this amount of anticorro-
sion/antifreeze.
If the coolant level is low, water and
MB 325.0 Anticorrosion/Antifreeze
should be used to bring it up to the proper
level (have cooling system checked for
signs of leakage). Please make sure the
mixture is in accordance with label
instructions.
The water in the cooling system must meet
minimum requirements, which are usually
satisfied by normal drinking water. If you
are not sure about the water quality, con-
tact an authorized Mercedes-Benz Center.
!Add premixed coolant solution only. Adding
water and MB 325.0 Anticorrosion/Antifreeze
separately from each other, could cause engine
damage not covered by the Mercedes-Benz
Limited Warranty.
Page 455 of 473

454 Index
Combination switch 113
High beam flasher 113
High beam headlamps 55, 113
Low beam headlamps 55
Turn signals 55
Windshield wipers 56
Control system 121
Control system menus 124
AMG 128
AUDIO 133
NAV* 135
Settings 136
Standard display 127
TEL* 149
Trip computer 148
Vehicle status message memory 135Control system submenus
Convenience* 147
Instrument cluster 139
Lighting 143
Time/Date 141
Vehicle 146
Convenience opening/closing*
Power windows 238
Retractable hardtop 244
Coolant 448
Adding water 293
Anticorrosion/antifreeze 449
Checking coolant level 300
Messages in the multifunction
display 368–370
Technical data 444
Temperature 289
Temperature gauge (Multifunction
display) 127Corner-illuminating front fog lamps* 114
Replacing bulbs 393
Cruise control 247
Messages in the multifunction
display 358
Cup holder 254
Curb weight 328
D
Date (Control system) 142
Daytime running lamp mode 111
Setting 143
Deep water see Standing water
Defrosting
Rear window 170
Windshield (Automatic climate
control*) 188
Windshield (Climate control) 177