patelmd

I have an 02 Audi A4 B6. My car was overheating and it lost heat. I replaced my thermostat and it fixed my overheating issues but im still not getting any heat. when i rev the engine over 3000RPM or drive on the highway i am getting fair amount of heat. i bled the the cooling system like 5 times and still not getting heat. are their any other bleeder valves except the one by the injectors? note that i was getting heat before the the car was overheating.
thank you in advance.

Edward6420

I had an issue with a 2002 A4 that had no heat. The Audi system for cabin climate blends hot and cool air 100% of the time to maintain the "set tempurature". This causes the heater core to function all the time. What happens, over time and thousands of hot / cool cycles is to break free thousands of small sand particles from the sandcast engine parts that collect in the very small webs of the heater core. There is also accummulation of deposits that collect on the webs of the core (kind of like crust collects on a coffee maker or bathtub with hard water).

There is another post on this site that explains in great detail how to backflush the heater core to remove much of the debris and scale from the core which will allow more of the surface area to be exposed (more surface area = more heat exchanged = more heat in cabin).

My Audi has 153,000 miles and I flushed the core using CLR to break up the scale using a pulse from the hose and went from "see my breath" heat (I live in Michigan) to "my eyes are dryed out" heat with one treatment. The alternative is to change out the heater core which not only takes 12 hours of labor at $75 to $100 per hour but also introduces tons of rattles into the previously intact vehicle. Bleeding the cooling system only gets rid of probably good coolant. You need to remove the debris especially on older Audi's and never use anything but G12 and never mix coolant, ever.