I used to have an 89 W124 that would give this gurgling sound somewhere inside the dash area when the system is running. Apparently MB issued a kit that would fix this. On my 95 W124, this has not been a problem so maybe MB updated the design.

So back to older W124s, is it just drain & fill the coolant? Would there be any 'air pockets' that need to be purged, and how to do this?