Is it absolutly necessary to drain the cooling system before this can be replaced, as Haynes recommends? I searched through the threads on here and one guy mentioned that he did it without doing this? :confused:

I didn't when I changed mine, but it will need topping up afterwards.

I take it this was from leakage when you disconnect the pipe?

I've changed mine without draining coolant NOR topping it up!

After that I was driving for at least 1000 km and works just fine.

I drained about 1,5 liters and that was enough, just a few drops leaked

remember to squeeze a thick pipe goin' to radiator several times to remove air after topping the system, only then close the expansion tank!