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 392 of 474
391 Practical hints
Where will I find...?
The vehicle jack is located in the storage 
compartment underneath the trunk floor.
Storage position
Remove vehicle jack from its 
compartment.
Turn crank handle in the direction of 
arrow as far as it will go.
Operational position
Turn crank handle clockwise.
Before storing the vehicle jack in its 
compartment:
It should be fully collapsed.
The handle must be folded in (storage 
position).Setting up the collapsible wheel chock
The collapsible wheel chock serves to 
additionally secure the vehicle, e.g. while 
changing the wheel.
1Tilt the plate upward
2Fold the lower plate outward
3Insert the plate 
     
        
        Page 393 of 474

392 Practical hints
Where will I find...?
Tilt both plates upward1.
Fold the lower plate outward2.
Guide the tabs of the lower plate all the 
way into the openings of the base 
plate3.
For information on where to place wheel 
chocks when changing a wheel, see 
“Lifting the vehicle” (
page 414).
Spare wheel with collapsible tire
The spare wheel is located in the storage 
compartment underneath the trunk floor.
1Spare wheel, spare wheel bolts 
(located under plastic cover on the 
outside of spare wheel rim)
2Vehicle tool kit (under spare wheel)
3Retaining screwOpen the trunk (page 99).
Lift up trunk floor.
Loosen retaining screw3by turning it 
counterclockwise.
Remove spare wheel1.
Take off the wheel bolts for spare 
wheel1.
Storing the spare wheel with 
collapsible tire
If you wish to store the spare wheel after 
use, carry out the following steps. Other-
wise the spare wheel will not fit the storage 
compartment.
Unscrew the valve cap from the valve 
of the collapsible tire.
Take the valve extractor from the vehi-
cle tool kit (
page 389).
!Make sure the collapsible tire is dry when 
storing it. 
     
        
        Page 394 of 474

393 Practical hints
Where will I find...?
Unscrew the valve insert from the valve 
and allow the air to escape.
Screw the valve insert back into the 
valve.
Screw the valve cap back on the valve.
Pull the protective wrap provided with 
the vehicle tool kit over the spare 
wheel.
Store the spare wheel and the valve 
extractor in the storage compartment 
underneath the trunk floor.
Pierce the protective wrap with retain-
ing screw3.
Secure the spare wheel by turning 
retaining screw3 clockwise.
For information on mounting the spare 
wheel, see “Flat tire” (
page 408).
Spare wheel bolts
1Wheel bolt for light alloy rims
2Wheel bolt for spare wheel with 
collapsible tire (located under plastic 
cover on the outside of spare wheel 
rim)
iIt may take a few minutes for the collapsible 
tire to deflate completely.
!Wheel bolts2 must be used when mount-
ing the spare wheel with collapsible tire. The use 
of any wheel bolts other than wheel bolts2 for 
the spare wheel with collapsible tire will physi-
cally damage the vehicle’s brakes.  
     
        
        Page 395 of 474
394 Practical hints
Unlocking/locking in an emergency
Unlocking the vehicle
If you cannot unlock the vehicle with the 
SmartKey, open the driver’s door and the 
trunk using the mechanical key. Removing the mechanical key
1Mechanical key locking tab
2Mechanical key
Move locking tab1 in direction of 
arrow.
Slide mechanical key2 out of the 
housing.Unlocking the driver’s door
Insert mechanical key 2 into the 
driver’s door lock until it stops.
Turn mechanical key 2 counterclock-
wise to position1 until the locking 
knob moves up.
The driver’s door is unlocked.
Pull the door handle to open the 
driver’s door.
iUnlocking the vehicle with the mechanical 
key and opening the driver’s door or the trunk 
will trigger the anti-theft alarm system 
(
page 90).
To cancel the alarm, insert the SmartKey in the 
starter switch.
1Unlocking
2Mechanical key 
     
        
        Page 396 of 474
395 Practical hints
Unlocking/locking in an emergency
Unlocking and opening the trunk
A minimum height clearance of 
5.78 ft (1.76 m) is required to open the 
trunk lid.Insert mechanical key 3 into the trunk 
lid lock until it stops.
Turn mechanical key 3 counterclock-
wise to position1 until it stops,
and simultaneously
pull trunk lid handle 2 and lift lid.
Turn mechanical key 3 back and 
remove it from the trunk lid lock.
Locking the vehicle
If you cannot lock the vehicle with the 
SmartKey, do the following:
Close the passenger door and the trunk 
lid.
Press the central locking switch in the 
upper part of the center console 
(
page 103).
Check to see whether the locking knob 
on the passenger door has moved 
down.
If necessary, push it down manually.
The passenger door is locked.
Exit the vehicle and close the driver’s 
door.
1Unlocking
2Handle
3Mechanical key
!Always make sure there is sufficient over-
head clearance.
 
     
        
        Page 397 of 474

396 Practical hints
Unlocking/locking in an emergency
Insert mechanical key 2 into the 
driver’s door lock until it stops.
Turn mechanical key 2 clockwise to 
position1.
The driver’s door is locked.
Turn back mechanical key 2 and 
remove it from driver’s door lock.Manually unlocking the gear selector 
lever (automatic transmission*)
In case of power failure, the gear selector 
lever can be manually unlocked, e.g. to tow 
the vehicle.
1Gear selector lever cover
2Release
Insert flat, blunt object (e.g. screw-
driver) into the left edge of cover1 at 
the position indicated by the arrows.
Loosen cover1 using this object.
Using your hands, pull cover1 out 
and remove.
Push down and hold release2 in 
direction of arrow.
Simultaneously move gear selector 
lever out of positionP.
The gear selector lever is unlocked 
now.1Locking
2Mechanical key
iThis procedure does not arm the anti-theft 
alarm system, nor does it lock the fuel filler flap 
and the storage compartments.
iThe gear selector lever is locked again as 
soon as you place it in positionP again.
 
     
        
        Page 405 of 474

404 Practical hints
Replacing bulbs
Low beam bulb (Halogen headlamps 
only)
Turn housing cover1 counterclock-
wise and remove.
Turn bulb socket5 with the bulb 
counterclockwise and remove.
Pull the bulb out of bulb socket5.
Press the new bulb into bulb socket5.
Place bulb socket5 back into the 
lamp and turn it clockwise.
Reinstall housing cover1.
High beam/high beam flasher bulb 
(Halogen headlamps) / High beam 
flasher bulb (Bi-Xenon* headlamps)
Turn bulb socket3 with the bulb 
counterclockwise and remove.
Pull the bulb out of bulb socket3.
Press the new bulb into bulb socket3.
Place bulb socket3 back into the 
lamp and turn it clockwise.Front turn signal bulb
Turn bulb socket2 with the bulb 
counterclockwise and remove.
Press gently onto the bulb and turn it 
counterclockwise out of bulb 
socket2.
Press the new bulb gently into bulb 
socket2 and turn it clockwise.
Place bulb socket2 back into the 
lamp and turn it clockwise.
Parking and standing lamp bulb
Turn bulb socket4 with the bulb 
counterclockwise and remove.
Pull the bulb out of bulb socket4.
Press the new bulb into bulb socket4.
Place bulb socket4 back into the 
lamp and turn it clockwise.
Replacing bulbs for rear lamps
Before you start to replace a bulb for a rear 
lamp, do the following first:
Turn the exterior lamp switch to 
positionM (
page 109).
Open the trunk lid (page 99).
Tail lamp unit
1Bulb socket for rear fog lamp 
(driver’s side only)
2Bulb socket for turn signal lamp
3Bulb socket for backup lamp