Found the MB citric acid radiator flush. Also learned that one drains system, fills with water and flush, runs to temp for 15-20 minutes, drains. Fills with clean water, runs to temp, drains and repeat water flush 3 times. Make sure heater is on so flushes heater core too.
Does this procedure jive with the experts out there? I'm going to give this a try along with a newer fan clutch to see if I can get my running temp down. I have a new radiator to install if all else fails, but would rather keep the original radiator and resell this aftermarket one. I don't relish the process of replacing a radiator.
I'll report back on the results.
Shawn Rock
Philly, PA USA
1968 280 SL 4 speed