Looked in the FAQ search and found nothing. In the regular forum search there are a zillion posts/replies and " this is what I did".
Is there a link to the MB process and recipe that is suggested? Maybe I missed it.
Here is why...
My buddies 80 240d runs great, motor heats up to temps and no overheating issues but we get very-very low temps on the heater. Figured we would do the Citric flush . I feel the heater core must be constricted with crap. When we put the fan on high it cools the coolant so much it comes out cold from the heater vents. Again the engine temps are fine and measured with a infared thermometer gun. The black rubber hose going into the heater is 160*f or higher so I know the hot coolant is getting there. Out the other side where the two hoses come through the firewall after it goes thru the heater are below 60*f. With fan on . Btw we put in a new Behr t-stat after getting great results on my 240. My 240 puts out the heat. You can dry your hair during a commute with my car.

Not going to pull the heater core in this life.. so what the next best solution or suggestion?

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81' 240d 4 spd 140k on the clock

Procedure is in the factory manual. Basically, you drain the system completely. Remove the thermostat and put the cover back on. Pour a container of the citric acid crystals inhte the cooling system and fill with water. Run engine with heat set to max defrost for awhile. Shutdown and drain system. Flush system with fresh water a couple of times. Drain system completely, reinstall thermostat and then fill with proper 50/50 mix. All told, a pain job to do right. You more than likely will get wet.

Another "quick and dirty" method is to disconnect the supply and return heater hoses and use a garden hose to flush through the heater core. Start with low pressure water and see what kind of junk comes out. Make sure heat is set on hot so the heater valves are fully open. You will have to partially drain the coolant, so this may be a good time to replace the antifreeze if it's been more than a couple of years.

http://www.schumanautomotive.com/forums/showthread.php?t=264

Manual is very clear on requiring a deoil treatment before doing the citric acid descale treatment. And it is required whether or not there is evidence of oil in the cooling system.

Len