You also might try draining the system before replacing anything. Just to confirm there's no air pocket. Drain the system, then use a water hose and back flush the system to make sure there's no debris. Then refill the system. I would start filling the system, then turn the key on 2 position, engine not running, set the temp to max heat so the aux water pump is on then continue filling the system. This way it reduces air pockets. Once filled, idle car with heat on until operating temp is reached and see if you still have the issue after driving a few days.....or purposely try to force an overheat by idling with the ac on under load. This way, you're able to just shut it down if it starts to go excessively high or even get a water hose across the radiator to bring the temp down. I'm actually doing my 201 right now as I write this because I had to replace the expansion tank 😂

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1990 190E 3.0L