Okay I have read other posts about this issue and I have done the heater core flushes 3 times now each time getting gunk out the last time I got a massive chunk of stuff out and heater worked great for about 2 hours then went cold again. I have bleed the air out multiple times as well nothing is keeping the heat going. I have a Audi A4 2003. Any other suggestions? I am going to do yet another flush tomorrow and see what happens but I want something that is going to make the heat stay it's been well below zero here the last week and it's not fun driving a freezing cold car. The temp gage stays within range so it's not overheating. Please help.