Ford Focus water tank emptying suddenly

[iwin11]

Hello there:

Can anyone help me with advise and info please. My car recently developed a problem of engine coolling water suddenly falling dramatically below min level over night. I would look up water level every few days and top up well above max level since this problem developed. But while two days ago the water was still above max (and having maintained at this level for at least a week), two days later it suddenly sank well below the min level. After I topped up, the water would remain stable for 1-2 weeks, and one day it would suddenly drop a great portion. What is the likely problem and what should I do? Thanks for any help!

Make: Ford
Model: Focus
Engine size/Type: Zetec 1600
Year: 2000
Mileage: 65000

Chris

 

[Burnerman]

At this stage, look for crusty deposits at the end of each hose, the top and bottom radiator connections and also similar signs of overflow at the expansion bottle filler cap.
Are there any signs of coolant on the ground or car floor, or any unusual smells either inside or outside the vehicle?
Pay particular attention to the side of the engine, drivers side near the bottom - the water pump lives down there.
Keep the coolant level exactly on the maximum when its topped up, and post back!
John