You can flush it that way but due to the way the system is plumbed (some coolant in the system is below the drain) you will need to drain, refill (demineralized water is fine), idle the engine for like 45seconds, repeat. It takes like 7 cycles of this for the drained fluid to get pretty clear.

Better is to get a Prestone flush-n-fill kit; install; follow instructions to flush with garden hose. Unless your tap water is really hard once you have flushed you can refill with HOAT and demineralized water. A 50/50 mix is best. Don't fall for the expensive scam of buying pre-mixed antifreeze just get the straight good stuff. NOTE the manuals are inconsistent on coolant capacity probably due to bad metric to US conversion; best guess is system capacity is 13 US qts; my recommendation is add 6.5qts to a drained system and then fill to top with demineralized water which should get you to ca. 50/50 when you consider the fluid that did not drain from the system.

Getting the best mix is the most important though, the best protection and performance is actually at above a 50/50, it is more like 66%. So if you flush the system entirely and drain from the bottom, you will get about 2 gallons back in, leading to a nearly perfect 60/40 mix. This is what I aim for with the CRDs I work on.

The other thing to remember is that diesels naturally will want to run COLD, and the thermostat is actually causing it to run hotter (to the design spec of the thermostat) than it would normally.

Gasoline engines: When working hard and getting hot, add more fuel to "cool" the combustion chamber, or risk melting a piston. Idling a gas engine causes heat to build up b/c of low(er) fuel consumption. Idling gas engine must stay at 14:1 air:fuel, so uses gallons per hour. Lean burning is hotter. Rich burning is cooler.

Diesel engines: When working hard and getting hot, REDUCE fuelling to cool the combustion, or risk melting a piston. Idling a diesel causes heat loss, due to extremely low fuel consumption. Idling diesel can go to greater than 250:1 air:fuel, and a 4-cylinder 2.8 liter diesel with the AC on uses about a quart per hour. A 1.9 liter diesel (VW) idling uses about the same. Just enough fuel is burned to keep the engine rotating, leaving almost no waste energy to heat up the water. Lean burning is cooler, rich burning is hotter.

Geordi is correct, 66% ethylene glycol / 34% water is the best for freeze protection to -60F. 50/50 offers freeze protection to -38F. But.......ethylene glycol does not shed heat nearly as well as water. This means that running a higher concentration of glycol can reduce the cooling capacity of your vehicles cooling system. Therefore, I suggest using a 50/50 glycol/water mix for all but the most northern states. Did I mention that I am a Production Specialist for the Ethylene Oxide / Ethylene Glycol plants for a major petro-chemical company at one of their manufacturing complexes?

Just an FYI.......If you think 100% glycol will offer better freeze protection than 66%/34%, think again. 100% ethylene glycol freezes at +8F.

Yeh, perhaps "scam" was not the most appropriate term for me to use. Just to be clear I consider 50/50 pre-mix generally way over priced considering it's 1/2 good stuff and 1/2 demineralized water that often costs all of $1 at the local grocery store. It does work but...

It will be best to totally flush your radiator. You can do it at home with distilled water. Just fill and drain until the coolant coming out is clear. Then you can fill up with zerex g05