If the engine is at 80C & you still don't get heat take a look at the FIRST post that I made!! as we replace heater (duo) valves on these cars all of the time!
NO reason to replace t-stat if the engine gets that hot.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)