A4 coolant loss
 

Can anyone help me. I own an Audi A4 Avant SE TDI 110 having done 127000 miles. I have already taken the car to 5 different garages but nobody seems to be able to sort it out! Some 9 / 10 months ago I noticed that it was loosing some coolant especially on long journeys at high speeds (0.5 litre after 300 miles). This continued for some 3 to 4 months until one day I noticed that the water colour had changed dramatically form blue anti freeze colour to very dark brown. At this point I started to loose more water (1 litre every 15 miles) noticing that it was coming out of the header tank overflow. I changed the radiator cap with no effect. It got worse and especially when I was towing a caravan I was loosing substantial amount of water. The garage advised me to change the radiator as they did not suspect the head or the h/gasket. The problem certainly reduced and I could now tow some 100 miles without the coolant warning light coming on. The water is now clean Still not sorted I have now changed the water pump and the thermostat but even now after some 350 miles I still loose approx 0.75 litre of coolant non towing. The odd thing is that if you release the rad cap slowly some of the water returns to the header tank After numerous tests not one garage believes it is a head problem. Any ideas please??

RE: A4 coolant loss
 

Not sure about TDI.

but either it is leaking into the engine through a head gasket, or is leaking elsewhere. Have you checked for a crack plastic expansion tank? For gasoline cars, there is I believe there is a test to check for exhaust gas in the radiator that would indicate a head gasket. Have you just parked the car and let it run to see if coolant is leaking underneath?

No deisel Audi's are imported to the US, so most of us have little experience with this model. You may get more help on a VW forum.