I have a 2000 audi a4 with a 1.8 turbo and the heat operates very poorly. I have read about this problem extensively on this site. I know that the heater core is not blocked cuz i blew it out and the air blew out and both the heater hoses running through the firewall are hot when car is running. I just got my water pump replaced 10k ago and the heat worked last year....do not have a overheating issue or anything like that. I thought that is must be some air in the heater core...so i tried to bleed the cooling system through the hole on thehose coming from the heating core. I tried and tried but no fluid would come out of the hole...eventually i gave up and just pulled that hose with the bleeding hole off from the heating core and the flow coming from the heating core was very poor (flow took up about 20 percent of the pipe)...so just to make sure i tried to blow out the heater core again and it seems i am getting very good flow through the core...I think i got a blockage before the core in the system...so i flushed the system and i still have the same problem. I think that i must be getting decent flow through the engine cooling cuz my car is operating at the correct temperature. When the water pump was replaced the fins where just about completely gone...any chance that those plasitc pieces clogged up my system? Please any advice would be great. Forgot, i just replaced the temperature sender which did not help