I would bleed it if I were you and recheck it..

Mohamed, you didn't tell me what year your MB is but yes you do have to bleed the cooling system when you flush the coolant. There should be a bleeder valve(looks like a small nut with a snout) on the top of the intake manifold or at the thermostat housing, get the engine to operating temp and with the engine running slowly open the bleeder, you should have air bubbles with spurts of coolant coming out, when it stops spitting air you can close it and fill the coolant back to the proper level. Hope that helps you out.