Anti-freeze dilution during coolant change

[aspire_helen]

This must be common to many engines. Recently, I changed the radiator and coolant. I followed the Citroen refill procedure to the letter, backed up with Haynes Peugeot406 for the 2.2HDi DW12TED4 engine. I drained out a little over 5 ltr from lower radiator hose, with heaps of sediment. I could not access the cylinder block drain plug, which even Haynes state is virtually impossible. I flushed through the engine with water, as instructed, via the top hose with the thermostat removed. The hose water pushed out ahead of it some 3 to 4 ltrs of clear pink coolant (no sediment), before the clear tap water appeared. Of course, that means that the engine now contains 3 to 4 litres of tap water. Not surprisingly, on topping up, it only took 5 litres of coolant - Halfords ready mixed OAT coolant giving -37degsC protection. However, the final strength would be much less. Indeed, after the coolant had fully mixed, I measured it at the expansion tank at only -20degsC.
Regarding the engine block drain plug. Even if this removed, it does not drain the heater matrix, water pump and lower hoses.
My point is that neither Haynes nor Citroen (or Peugeot?) point this out...... (1) that a high percentage of the resultant coolant could comprises the flush water (ours is "very hard") (2) the anti-freeze protection is much reduced (3) the level of corrosion protection is reduced.
My advice would be to flush through the engine block with 5ltrs of ready mixed coolant (NOT tap water). This would ensure that the engine block is full of full-strength coolant and de-ionised water. If the radiator is re-used, it can be flushed with tap water and drained. Then use a second 5ltrs of the ready mixed coolant for the final top up.
Or am I missing something??????

[MattBLancs]

I've never used ready mixed coolant, only ever concentrated.

I normally flush very thoroughly with the hose "until the juices run clear" (or is that cooking a chicken? ) then reverse flush, back through radiator, sometimes disconnected heater matrix hose(s) too and flush that separately.

At test point there is neat water everywhere stuck anywhere if would not drain down from.

Refilling, I work out from the concentration chart and Haynes stated capacity of the cooling system, how much concentrated coolant to chuck in. Add that and top with water. Normally not much water at all. Say 1 to 2 litres where from the maths: assuming was empty, would be more like 6 or more litres expected.

[PaulC5]

I have only ever used concentrated coolant since it is not possible to get all the old out. The conc stuff goes in first and then top up with water. Also buying ready mixed you are buying water and more plastic containers than necessary.

[aspire_helen]

Buying ready-mixed you are buying de-ionised water without the damaging dissolved salts in tap water.