Hello everyone. I have problem with my Audi, (176kW), 2009 model year. The car has nearly 94 000 miles.
When it is warm outside it takes ages to get warm, when it gets cold, no matter how I drive the engine won't get warm. I've had diagnostics and it was all right, at least the guy told me the sensors were okay. I've had thermostat changed, but it didn't help. I am desperate, the car does not heat and I am worried about the DPF filter (the regeneration cannot start, because it never hits 90 degrees). I read here, on your forum, that it is possible to vent (to put the air out of the cooling system) but I don't know how it's done and whether I can do it at home ( I just hope the whole front won't have to be taken off as it was with the thermostat). I also noticed that level of cooling fluid is dropping but I haven't found any leaks and when I tried, after some driving, to take off the cap, it sort of popped out, as if it was pressure in the cooling system.

I am very sorry for my english, I am not native speaker. I will be forever grateful to anyone willing to help me with my problem.

PS: The water pump, timing belt and the thermostat, are all brand new.