x2. Cooling system capacity is dependent on pressure to a point. More pressure is more capacity until you get to where the water pump can’t do it’s job. I drove a 603 for a while with the cap loose when there was residual pressure. It worked for just getting around. On hot days and under load I had to keep an eye on the gauge because it would climb quickly. My SDL cracks got so bad that it took a few minutes from cold start to beyond 100*C on the gauge and rock hard hoses but the radiator was cold. Same water pump and thermostat did their job after I replaced the head.

Sixto
98 E320s sedan and wagon
02 C320 wagon