Coolant change help please

[darrsi]

Radflush? How does that work? Does it dissolve any crap in the system?

Radflush is basically a descaler that will remove hard water deposits that build up on the walls of the waterways restricting the proper flow of coolant.
If the coolant can't flow properly it'll overheat and any excess coolant will get pushed back to the expansion tank.
If they're really blocked the expansion tank will pressurise with boiling fluid then just overflow onto the floor.

When everything's flowing and working correctly the level in your expansion tank should more or less stay the same level, with maybe the occasional very small top up every 6 months or so.

In that respect the expansion tank is a good guide as to whether you have any issues at all, either by a blocked system or by a leak.