2002 1.8 T Quat 94000 kms. When I turn on my car in the morning everything seems fine. Once driven after about 10 mins I start to hear a sound in the engine, the sound is in the back of the engine near the cam chain. Could this be a sludge problem or cam chain tensioner. I opened the cap while car is on and there is no oil squirting out. I changed the oil three times in four weeks. Still the same sound. I had my mechanic inspect it, he took the rocket cover off and check the chain if loose but wasnt.

Once the engine is in idol it makes that tututututut noise. Once i take off and start driving the noise is gone then when i stop again it makes the same noise. The mechanic suggested that there seems to be dirt in the engine caus the oil hadnt been changed for a while by the previous owner. He suggested every 200 Ks u should change the oil to clean that dirt at least two times. Plus we called audi and used their suggested oil and factory filter.

What could this sound be?
Thanks

...and all the pieces get sucked into the oil pump pick up. Expect an oil pressure light soon.