Hello, I have a 807 2003 2.2 HDI with 110K on the clock. I've had the car for over a year and since I've owned it I've replaced the CAM belt as well as water pump. Naturally at that time I would have put new coolant fluid in the system. I've driven the car for over 10K miles without any issues, however from time to time especially on long journeys I notice a low coolant level warning flash on the dash. When I open the expansion valve cap with engine cold I notice quite a bit of air pressure being released and the coolant level rises automatically to the correct level. I don't actually need to top it up. The engine operating temperature holds well and I never noticed either any coolant loss nor and over heating. The car appears to have good service history. Any suggestions on what could be causing this condition? Should I check that the correct radiator cap is fitted perhaps even replace it as a pre-caution? Could it be that I put the wrong grade of coolant when I replaced the W/P? note: I bought all the parts from Eurocarparts according to my numberplate. Is it a sign of weak rubber coolant hoses which are about to burst, or is it something more sinister such as the start of a head gasket? Any suggestions and comments welcome. Thanks.