As i said mine took 7 ltrs of coolant and around 2ltrs of water. Its fine to take the cap off (well in my case never seemed to pressurise much, see previous post) to top up, also i found it was fine to run the engine with the cap off, still idled bang on 800rpm.
Ah i thought you said 7 litres of coolant and the rest water, with the capacity being 12 litres
Sorry couldn't recommend or see any reason to leave the cap off - when all that is necessary is to part tighten the cap initially, run it till fully warm, check then top up - as pressure builds up in the system as it becomes warmer hence you run the risk of the coolant spilling over the filler & possibly air finding its way in.
OK, heres how it went.....
Yesterday evening i successfully completed the coolant drain (my first one!), took a bit longer than expected due to some seized bolts on the plastic underbody shields
But got there eventually and was left with an empty system & a couple of buckets of rusty coloured coolant.
Next i ran the hose into the filler cap until the water ran clear, then closed the drains and filled up on water & coolant flush.
Today i drove to work and back with the flush in the system to give it a good clean out, then drained it & got the hose through it once again when i got home.
After that i changed the thermostat (easiest job of all) and put a new filler cap on before filling up with some good quality coolant
With this all done it was time to take her out for a really good run to see if the problem was resolved and SUCCESS!! She is back to normal & running perfectly
I will be keeping a close eye on her for a while but fingers crossed, everythings back how it was.
Thanks for all the advice on the matter, very much appreciated!
Well done - its a bit daunting first time round with the bleeding , but not really such a bad job to do - and at least you know its been done correctly, garages are terrible at bleeding the system correctly afterwards!!