2007 Mercedes SLK-Class Owner's Manual - Page 302

Operation Engine compartment The coolant expansion tank is located on the passenger side of the engine compartment. Using a rag, turn cap 2 slowly approximately one half turn counterclockwise to release any excess pressure. Continue turning cap 2 counterclockwise and remove it. The coolant level is correct if the level for cold coolant: reaches marking bar 3 in expansion tank 1 for warm coolant: is approximately 0.6 in (1.5 cm) higher Add coolant as required. SLK 350 (example illustration) Using a rag, slowly open the cap approximately 1/2 turn to relieve excess pressure. If opened immediately, scalding hot fluid and steam will be blown out under 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. Replace and tighten cap 2. For more information on coolant, see "Coolants" ( page 448). 1 Coolant expansion tank 2 Cap 3 Marking bar in the expansion tank 301