bmorin

i have a 2005 audi a4 1.8 avant quattro with 139,000km and i recently lost my hot air when the heater was on.
i took it to the mechanic and he said there was a blockage and he flushed the heater core and it was blowing hot air for a couple hours and then it was very weak and mostly just cool air blowing. i drove it to get an oil change because it was due. and he said that it looked like the same old rad fluid was used that the other mechanic said he flushed out. so he removed a blockage but kept the old ****ty rad fluid in it. anyways . i paid the guy at the oil change place to flush the system . and my heat was working again for about 20 mins and then it was weak again. so is my heater core shot or do i need to replace my timing belt,water pump, thermostate and tensioner, etc....$$$$

A1EK

This is a very common issue from reading the posts and I can talk from experience as I had the problem. It took me weeks to resolve the issue, I lot of searching and trying different things, but it came down to flushing and removing the trapped air that worked for me.

First was the old coolant emulsified and sludgy? If so then you should flush the heater core and expansion tank again. The best way to flush the heater core I found is to find the inlet and outlet pipes next to the battery at the back of the engine behind bulk head. Remove the clips and pull off the hoses, if they are tight, try pushing them first then pull off I think the top pipe is out and bottom is the inlet. Now heres the trick, if you can connet your garden hose to your house hot tap (I made an adaptor) this will greatly help disperse the gunk, connect to the inlet of your heater core and let the hot water flow through for a few mins. Now connect the hose to the outlet of the core to back flush, the gunk will come out of the inlet pipe now. Do this a couple of times then the same for the hoses you removed that go to the engine, you can open the radiator drain to allow the water to exit there.

Once you have flushed properly, clean your expansion tank, remove from the car by unplugging the cable and use a little washing up liquid or spirit to get rid of the gunk and flush out. Now re-connect the core hoses, close the radiator drain and fill the car with preferably distilled water or pre-mixed pink coolant to the correct concentration.

The challange now is to bleed the air from the coolant system, start the car with the heater on full then after a few mins pull back the inlet pipe at the core and you'll notice a small 2mm hole in the hose, this allow you to disperse air and keep the hose connected to the pipe. You are looking for a steady thin spray of coolant, but first you will see bubbles. Hopefully this should fix the no heat issue, if not then remove the engine plastic cover and there is a metal pipe on the right top of engine with either an Allen key or nut, loosen this when the engine is warm and allow the air out. Drive the car and repeat the process at the engine pipe, it took me a bout 3-4 times before all the air was gone and I had heat.

Good luck, if you get it right your car should start getting warm inside after 3 mins, and stay warm when sitting at the lights and not go cold !

lyleswk

AE1K, great post!