The engine makes clicking sound, knocking noise when car is standing after few minutes. the noise goes away when rpm's go up or when car is driving. it is 2001 a4 turbo manual. can it be cam chain tensioner and if yes does it make sense to fix it at 124000 miles. how much would it be??

SOURCE: A4 2001 turbo diesel front brake kncking sound

check if your sensors are fitted back in their holders they maty be hanging loose or your dustcover behind the brake disc needs to bent straight

SOURCE: knocking when first start engine

Depending on the period of time and intensity of the knock ? If it is a rapid short ,loud knock then disappears altogether you may be dealing with a cam chain tensioner that is loosing oil pressure when the car is standing. A loose cambelt tensioner can increase the noise .

SOURCE: 2001 Audi A6 2.7T

VERY POSSIBLE THAT IT IS ONE OF THE TURBOS THAT IS GOING OUT. WILL HAPPEN IF POOR OIL SERVICE. ALSO CHANGE YOUR OIL WITH A SLIGHTLY THICKER OIL IF OVER 80,000. I OWN A 01 2.7T WITH 89,000 AND USE ROYAL PURPLE SYNTHETIC 20W-50

SOURCE: Banging noise coming from engine

There are 3 possible reasons the oil light would go on. The 1st and 2nd reason would be due to no oil lubrication of engine components. This could be from a failed oil pump, or critically low oil level. The 3rd possibility would be a defective oil sending unit giving a false reading of a problem. You should always immediately pull over and shut the vehicle off if the oil light goes on, as driving the vehicle could result in severe damage to the engine. The banging noise you hear and the black smoke is probably due to a major engine problem, due to lack of engine lubrication. How much oil did you have to add to bring it up to full level?

SOURCE: turbo= not working

Most likely the turbo is gone. What ever part of the turbo went, just replace the entire turbo. Not serviceable 99% of the time. The engine will not like being driven for any extended period of time with a bad turbo.