I HAVE A COLT 2.8 tdi AND HAVE REPLACED RADIOTOR, WATERPUMP AND RADIATOR CAP AND NO LEAKS WERE FOUND. AFTRE ABOUT 60 TO 80 MILES I HAVE TO FILL UP WITH ABOUT 400 TO 700ML OF WATER. IF I FILL UP WHEN IT IS COLD AND LEAVE OVERNIGHT I NEED TO PUT IN ABOUT 200ML.
WHAT CAN THE PROBLEM BE AND WHERE SHOULD I START LOOKING
You ARE losing coolant so you need to pressure test the cooling system to determine where it's going. You may have gotten it a little too hot in the past and have a head gasket problem now. They can run chemical testing to look for that but pressure test first.