Hi, dont post much on here but i need help!! lol

My brother has a 2001 Mondeo 1.8 Zetec (Duratec engine), and its gained a few problems all at once!

- For a few weeks, the car has completely lost power at all revs.
- It has got a slight knocking noise coming from the top end of the engine.
- When first started or when revved slightly (to about 2k revs), you can hear water flowing really clearly (sounds like it comes from under the dash), doesnt sound healthy!
- Sometimes takes a while to start, ie engine turns over about 5/6 times before starting.
- And also you can see air bubbles raising in the header tank (dont know if this is normal or not).

Any help really appreciated as my brother is getting really annoyed with the problems at the moment!!

Thanks

Ste