Hi, Here is what has happened to my Xantia Break 1.9TD In the beginning I have found some oil on the coolant filler cap, but the engine was fine, no overheating or anything else, it was not loosing any obvious quantity of oil... Maybe a month later, while travelling, the engine started to overheat and when I checked the radiator,it was absolutely cold. Trying to get home I disconnected the A/C Bitron plug (to make the radiator fans work at full speed) http://i132.photobucket.com/albums/q23/Clogzz/Pressure_switch.jpg and switched on the A/C to the maximum temperature and blower speed. It helped for a while - the temperature was slightly above 80 deg celsius, but after a few kilometers the heater started to blow freezing cold and the coolant together with plenty of oil erupted through the coolant filler cap. I am writing here to help others because the problem is maybe rare and the only place I've found to mention it was here. But there it is discussed quite well and helped me a lot. There are two possibilities for the leak of oil into the cooling system. The first (and the cheaper) is defective oil cooler, which I have already checked and changed, as it had a hole, but it did not help. And the only other possibility is a problem with the cylinder head gasket, or the head itself. Now I am saving money to go on with that other (more expensive) possibility. For more information click here (https://www.youcaring.com/myfamily-733336), preliminary thanks, any help will be highly appreciated. Best regards and wish you safe and smooth driving, Dimitar