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Hi gang, Long time lurker, seldom poster here. I've searched the forum and can't find a match to my case so I thought I would post the question to see if anyone can help. I have a 2015 A6 Avant, 200kw, 3.0 tdi with about 100k on the clock. Never missed a service and has always worked like a charm. I am not the first owner but have put the last 30k or so on it. It came to me with FSH (not all main dealer). Now a few weeks back I was on a relatively long and spirited drive back home from Oxfordshire when I noticed the engine was overheating (warning light on and torque limited). I pulled over and immediately upon slowing down the car started to cool down again. I checked the expansion tank and I wasn't low on coolant. As the car had cooled down again I thought I'd just drive a bit more judiciously for the remainder of my journey which worked just fine. A couple of weeks after that, I was driving to work at motorway speeds and noticed the car heating up, this time only by a couple of LEDs over 90c on the dial. Again, it cooled back down to 90c when I slowed down to about 50mph and cruised like that for a while. This seemed to be getting more frequent so I took it to my mechanic. As the car never overheats on idle and only overheats when driving at speed, he suggested it was the water pump as opposed to the thermostat. He changed the water pump for me but the problem still persists on journeys over about 25 minutes in duration. Even stranger, last night I went for a drive to confirm this, as I hadn't had a longer journey for a week or so, the engine heated up as described above. I then put the cabin heater on full blast and HI heat for a while and the temperature came down rapidly and stayed at 90c regardless of my speed. All very peculiar! Has anyone experienced this before or does anyone know of what could be causing this issue? I've spoken to an Audi specialist who thinks either the new water pump was faulty out of the box or the thermostat might actually be the problem, even though the symptoms aren't typical (if such a thing exists). I did speak to him before my experiment last night though, so he doesn't have those details. I'm at my wits end trying to figure this out so any help and guidance from those in the know here would be much appreciated! memzey

I recently purchased a audi A4 B6 2.4 petrol. The problem I have is the coolant starts to pour out of the expansion tank when it starts to get hot. The temperature is ok it doesn't go above halfway. Ive had the water pump, timing belt, thermostat and the head gaskets changed but nothing has made a difference. I'm lost to what this may be, can someone please help