Just a quick question about my pressure cap. Because of the bad weather the car didn't move for a week. I left the fitting in the neck of the bottle (see photo in first post) and put the cap back on, although no resistance of course. Anyway, I went out to get a new cap (£9.90 from my local Vauxhall parts man) but on a dual carriageway on the way back I noticed the engine/steering wheel juddering at 40mph+ and when I got home the cooling fan was on (very rarely comes on). Is this linked to my engine pressure do you think? I'll have a go at putting the new cap on when everything has cooled down in there.