Over heating after 30 minutes drive on 1990 Mercedes-Benz 300E

Needle goes up to red after driving in moderate traffic for 30 minutes. Engine does not let off steam when this happens.
I top up with coolant, about two cups after 30 minutes drive on mornings and same on evenings.Seems as though it is getting worse since the warning light now comes on.

1 answer
you cannot continue driving the car when it overheats; you will permanently damage the engine. strongly suggest towing the car to a local MB specialty shop and let them diagnose this problem for you.