Do you have working heat?

Can you try bypassing the heater core? Cap off the metal pipes running to the firewall. One near the oil filter and one going to the mono valve.

My 300 SD ran hot even after a citric acid flush. I had to replace the 26 year old radiator.

Radiators.com has one for the 300SD for around $200.00

__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf ‘86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad