Update: After topping it up with a few more L of coolant, its now NOT loosing it at such an alarming rate! I accidently left the bleed screw slightly undone while driving it to work, and I suspect allowing it to get hot & at high rpm with the screw undone forced some trapped air out of the system.

Hello! I've recently finished rebuilding the head of my TD5 after a lifter went. Most things were replaced at the same time (gaskets, inject seals, all bolts etc). It's now loosing a fair bit of coolant with no obvious leak. There is some white smoke on startup, however after a minute or two...