'88 190E 2.6... I need to do a coolant change.

With the engine off I assume there is no vacuum to the heater control valve, and if this is the case, is the valve open to allow coolant to drain from the heater core, or do I need to remove the cowl screen and apply a vacuum to open the valve.

I had to replace it about 15 years ago, but, unfortunately, threw the old one away.

Duke