I've got a 2005 Ford Focus. A few weeks ago it started juddering and the engine light was flicking intermittently. My mechanic found lots of brown, horrid water in with the spark plugs, which were very rusty. He replaced those and the HT leads, which seemed to solve the problem.

A week later it started juddering again. This time there was pink liquid in with the spark plugs which was identified, using a Hydrometer, as engine coolant. He's identified it as a cracked head, based on crystallization he's found and a faint line on the head. I'm after second opinions as it's looking incredibly pricey to repair.