Hello. I have a 2003 a4 1.9TDI. A couple of months ago i noticed that the car temperature was only going up to about quarter the way, it wasn't reaching 90 so i replaced the thermostat. Since i did, the needle reaches 90 and everything seemed fine until a few weeks later the coolant light came on, i topped it up and it was ok for another few days until it happened again. I discovered that the vent hose that goes from the back of the engine to the coolant system was after melting where it is sitting near the back of the engine(without actually touching the engine). I replaced that hose and after a few weeks, it is happening again. There seems to be alot of heat coming off the engine and melting the hose i was wondering if someone may have experienced this before or if someone could have any ideas..