IMHO, to adequately flush the cooling system one must install
a prestone back flush kit. the "T" installs in the heater hose
coming from the fire wall. then....

1. loosen the top radiator hose from the top of the radiator. take a small oil cap (available from a car parts store) and plug the top radiator inlet. be sure to rest the radiator hose on the top of the radiator.

2. connect a garden hose to the "T" connector and turn
on the water full blast. run the water until it runs clear coming
from the top radiator hose.

3. do the diesel flush sequence shown on dieselgiant.com use the Shout
Ultra Gel mixed in two gallons of warm water. put this mixture into the radiator. tighten the hoses, remove the "T" connector from the garden
hose and close the system. start the car, run for 15 - 20 minutes
with the heater turned on high. afterwards, drain the water from
the radiator and then reinstall the drain plug. perform steps 1,2
above until the water coming from the top radiator hose runs crystal clear.

4. perform the mercedes benz citric flush. afterwards, perform steps 1- 2
above until the water runs crystal clear.

5. if you are unsure about the age of your radiator I recommend purchasing a new Nissens radiator with the improved design. you don't know the age of your current radiator. what if the transmission cooler barrier fails and the old radiator dumps coolant/water into your trannie?
now THAT is an expensive failure. makes the cost of a new radiator
look cheap compared to a transmission replacement.

6. LAST but not least is this: regular green antifreeze does not provide
sufficient cooling capabilities for a diesel engine. diesels get hot and
require an antifreeze SPECIFICALLY rated for diesel use. a lot of mechanics do not know this and will put green stuff in a diesel. WRONG.
either use Amsoil antifreeze which is rated for 750,000 over the road diesel use or Cummins Diesel has a special antifreeze for diesel engines. either
will get the job done and keep your engine running cooler. not using coolant specifically formulated for a diesel engine will shorten the life of your engine, I GUARANTEE IT.

7. use the stock thermostat, diesels run a little hotter than their gasoline
powered counterparts.