Page 302 of 474

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 456).Windshield washer system and 
headlamp cleaning system*
The windshield washer reservoir is located 
on the passenger side of the engine com-
partment.
SLK 350 (example illustration)
1Cap for windshield washer reservoir
Fluid for the windshield washer system 
and the headlamp cleaning system* is 
supplied from the windshield washer 
reservoir. It has a capacity of 
approximately 7.4 US qt (7 l). 
     
        
        Page 377 of 474
376 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
/Top Up Coolant
See Operator’s 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 378 of 474
377 Practical hints
What to do if …
Display symbolDisplay messagePossible cause/consequencePossible solution
±Display Malfunction
Drive To WorkshopCertain electronic systems are un-
able to relay information to the con-
trol system. The following systems 
may have failed:
Coolant temperature display
Tachometer
Cruise control display
Have the electronic systems checked by an 
authorized Mercedes-Benz Center.
NCheck oil level
when next refueling
.
SLK 280 and SLK 350 only:
The engine oil level has dropped to 
a critical level.Check the engine oil level (page 296) and 
add engine oil as required (
page 299).
If you must add engine oil frequently, have 
the engine checked for possible leaks. 
     
        
        Page 457 of 474

456 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 462 of 474

461 Index
Climate control 172
Air conditioning refrigerant 452
Air conditioning, Cooling 180
Air recirculation mode 178
Air vents 172
Air volume 177
Control panel 174
Defrosting 170, 177
Residual heat utilization 181
Switching on/off 175
Temperature 175
Clock 120
Cockpit 24
Cold tire inflation pressure 331
Collapsible tire (spare wheel) 447
Collapsible wheel chock 391
COMAND* system 29
Driving instructions 287
Navigation 135
Combination switch 113
High beam flasher 113
High beam headlamps 55, 113
Low beam headlamps 55
Turn signals 55
Windshield wipers 56
Control system 121Control system menus 124
AMG 128
AUDIO 133
NAV* 135
Settings 136
Standard display 127
TEL* 149
Trip computer 148
Vehicle status message memory 135
Control system submenus
Convenience* 147
Instrument cluster 139
Lighting 143
Time/Date 141
Vehicle 146
Convenience opening/closing*
Power windows 238
Retractable hardtop 244
Coolant 456
Adding water 293
Anticorrosion/antifreeze 457
Checking coolant level 300
Messages in the multifunction 
display 374–376
Technical data 452
Temperature 289Temperature gauge (Multifunction 
display) 127
Corner-illuminating front fog lamps* 114
Replacing bulbs 400
Cruise control 248
Messages in the multifunction 
display 362
Cup holder 255
Curb weight 331
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*) 189
Windshield (Climate control) 177
Delayed shut-off
Exterior lamps 144
Interior lighting 145
Department of Transportation see DOT
Difficulties
Wile driving 58
With starting the engine 52 
     
        
        Page 467 of 474

466 Index
Manual transmission 153
Driving 53
Gearshift pattern 51
Starting with SmartKey 51
Maximum inflation pressure 332
Maximum load rating 332
Maximum loaded vehicle weight 332
Mechanical key see SmartKey
Memory function* 107
Menus see Control system menus
Messages in the multifunction display see 
Multifunction display messages
Mirror lamp* see Sun visors
Mirrors 168
Additional turn signals 401
Adjusting 46
Antiglare position 168
Auto-dimming* 168
Exterior rear view mirrors 46
Interior rear view mirror 46
Mobile phone see Telephone*
MOE tires* see MOExtended system*
MOExtended system* 321, 421
MON 292, 455Motor Octane Number see MON
MP3 210
Multifunction display 121
Multifunction display messages 360
ABS 362
Air bags 365–368
Battery, Vehicle 372
Brake fluid 373
Brakes 373
Bulbs 381–386
Coolant 374–376
Cruise control 362
Doors 371
Engine oil 377–379
ESP
®362, 363
Fuel 379
Hood 371
Low tire pressure 387
Maintenance service indicator 337
Parking brake 372
Passenger front air bag 367
Retractable hardtop 380, 388
Run Flat Indicator* 369
SmartKey 381SRS 364
Symbol messages 371
Telephone* 388
Text messages 362
Tire Pressure Monitoring System 370
Transmission 364
Trunk lid 371
Vehicle status message memory 135
Washer fluid 388
Multifunction steering wheel 28, 122
Heating* 276
N
Navigation system* 135
Neck-level heating see AIRSCARF*
Neutral gear position
Automatic transmission* 155, 157
Manual transmission 154
Night security illumination (Control 
system) 144
Normal occupant weight 332
Number, Vehicle Identification (VIN) 438