Coolant Flush on 1999 AGU lump. Some stoopid questions :)

[dai-cymru]

wasnt far off with -40 then  personally i would do 2:3 we are never likely to see -24 

[topher]

2 bottles of G12++ so 3L then 2L of that water. Would that be right? Then fill the whole system using that?

Stick with that plan, although you probably wont use it all as you can't drain the entire system. That way you can do top ups with water without worrying about diluting the mix too much.