Cooling System

Hi,

I have an A6 C6 2.0ltr TDIe with the CAGB engine, i am wondering if i have a problem or not.

Driving the car about or to work the temperature guage goes up to normal(90degrees) if i have the heater on the temperature guage starts dropping off 70 or sometimes down to 50, if driving on an open road speed about 60 -70 mph temp goes up to 90 degrees again and stays there, now, if i open bonnet and touch top hose its cold as is bottom hose, plastic pipe that attaches to top hose and connects to back of engine is coolish, heater hoses get hot,return to header tank is hot so is the bottom hose from header tank.

Some web sites say this is normal as it uses the coolant heat for the cabin first, but it just does not seem right to me, i have flushed the heater matrix using a hose pipe and no blockages, radiator runs clear, heater control valve is working, have plugged it into VCDS and no fault codes show for heating system, i am wondering if it needs bleeding still, but can only find one bleed screw on the heater return pipe under the skuttle panel, which runs clear of fluid and no air, does anyone now if this normal with no heat in the rad hoses, i cant seem to get a definite answer dont want to ruin the engine. Also no overheating either

Any Help Appreciated

Thanks Kevin