I had a good look at some of the suggestions posted and I found some dried up coolant on top of the turbo. It was coming from a hose that runs from the coolant reserve tank to the turbo, the hose itself looked like it wasn't pushed in enough onto the turbo. I pushed it in as far as I could and tighten the clamp. Hopefully that fixes it, but I'll keep an eye out and monitor it. Thanks for all the replies.