On a 300Tdi the gasket between the coolant pump and the engine block is a common failure (just replaced it on my 110) so possibly the same on a Td5?
The waterpump on a td5 is behind the power steering pump rather than being bolted to the engine.
Meh - just thought I'd mention it. BTW - I hate Td5s After trying to diagnose stuff 300Tdi is far simpler, 2.25D even easier...