Diffucult to guess without actually seeing it, we have a KA the same as that and I can't tell you 100% what it is. IF it just has two big pipes comes off it i would guess thats the power steering bottle as it only has a supply and return. In which case i'm sure it would be ok to drive it as long as it's just a bit of water in the system, I'd describe to you how to drain it but TBH if you've done that it's not something i think you'd be confident undertaking. Does it have anything written on the cap or a symbol?