You probably have something else happening. The 123 bodies have two serious leak points that come with age. Three actually. The first two are the wells where the hood springs are enclosed. They have drain holes, but if they are not cleaned of leaves and trash regularly, they rust out and the water drains through the rust holes into the front floors.

The second place is the battery box. It rusts through from the acid and the water runs straight to the passenger side floor. If the car is sitting level or with the front end a bit higher than the rear, the water runs to the rear floor.

These are almost universal problems with 123 Benz's.

Richard