2004 Mercedes SL-Class Owner's Manual - Page 260

Operation Engine compartment The engine coolant is a mixture of water and anticorrosion/antifreeze. To check the coolant level, the vehicle must be parked on level ground and the engine must be cool. The coolant expansion tank is located on the passenger side of the engine compartment. Using a rag, turn the cap slowly approximately one half turn to the left to release any excess pressure. Continue turning the cap to the left and remove it. The coolant level is correct if the level for cold coolant: is up to the upper mark on the bracing rib of the coolant expansion tank (translucent) for warm coolant: is approx. 0.6 in (1.5 cm) higher Add coolant as required. Replace and tighten cap. ! SL 600: Only open the cap on coolant expansion tank 1. Never open the cap between the two charge-air coolers. Otherwise, the engine could be damaged. For more information, see "Coolants" ( page 391). 1 Coolant expansion tank 259