What's the problem? Parts availability? It has to either be the master or slave.

A few years ago the clutch began dragging on my '88 190E 2.6 five speed. I figured
it was the slave, but since I change fluid regularly I was surprised. Upon looking at the removed OE slave the pushrod was mushroomed on the end. Upon disassembly the bore was perfect.

I got a new one from Pelican - even had the same casting number and was reasonably priced. Cleaned and greased the fork and end of the pushrod, and it's been fine ever since.

Hint: To bleed the system, open the slave bleeder valve and run a hose from the RF caliper to the slave. This bleeds it from the bottom up, so the air is quickly purged. If the brake fluid is of unknown age or dark, flush the brake system first so new fluid goes into the clutch system.

Duke