2001 A4 avant Quattro, 1.8T less than 70,000 mostly Highway miles. FOr months now has been making a ticking/knocking noise unpon cold start up. Starts up and drives fine, besides noise.
Mechanic 1 believes it's the starter (spring may be stretched/worn and not catching properly, since the noise isn't as loud if you turn car off and start again).
Mechanic 2 thinks it's low oil pressure and the wire mesh (?part name) at bottom of oil tank needs to be replaced.
Back story - Car used to get oil changes every 5 months or so up to 2008, then when bought to Audi dealer in new area I didn't realize they were only doing them once per year (car was in shop 6x over 2 years for other things). SO, due to that negligence Car was a victim of the dreaded Oil Sludge issue. Engine was Flushed and compression test was done - all seems fine. Noise started well before the flush, and has continued after. Mechanic 2 seems to think it's because the flush didn't remove the grime from the bottom of tank. Not sure which is more likely, the noise has been going on for over a year and doesn't seem to have any other affect on the vehicle - but after oil sludge issue I don't want to bust the engine if it's indeed related. Which is more likely?
If it's useful info -Timing belt and water pump were recently replaced also.
Thanks for any Info
Me

 

The screen you're referring to is on the oil pickup tube which bolts to your oil pump. It sounds like the car takes a minute to build oil pressure and get oil to the lifters in the head, (pretty common issue on the 1.8's, especially after sludge problems). I bet the car has slighlty low oil pressure from being poorly lubricated while the sludge was an issue. You can try pulling the oil pan and cleaning that and the pick up tube, but sounds like the damage is already done to me. Your low oil pressure light only comes on when it is dangerously low and almost non existent btw.

 

Thanks Faster,
I did have one person tell me that even though the damage is done (gaps created by oil sludge) that if the system is clean and oil pressure is maintained that the engine should run fine (even if I keep hearing the tapping noise upon start up) - But this noise seems much louder than simple tapping (possibly there are two seperate noises, and maybe I am not differentiating?). The noise had been going on for quite some time, and if it is indeed caused by Oil Sludge/Screen needing to be cleaned I am Agast that the horrible Audi Service people let this go on for so long (6 visits and they never took care of it), and even after doing the flush they didn't do a complete and proper job (I am not a mechanic and trusted them to take care of my vehicle - only ever going to Audi shops - but not anymore!).
This whole experience has turned me off to Audi's, even though I've loved the car prior to this.

 

Does the tapping sound go away after warm up?

It could also be the cam chain tensioner. Mine is shot and makes a very distinct clicking/tapping noise. Worse at startup, but never goes away at low rpms.

 

Lm,
It only makes the noise upon start up, and if you start the car and then turn it off and restart, the noise is much less.

 

Hm, may still want to check out the CCT. Could be a "cheap" fix, compared to pulling the pan and diagnosing a sludge problem. I could be totally off base, but it would seem unlikely that you develop a serious sludge problem in just 2 years. Have you been getting the low oil pressure light?

See if you can tell if the noise is coming from the back of the head, thats where the cam chain tensioner is. If you search for videos on youtube you should find some where you can hear what a loose CCT sounds like.

 

http://www.youtube.com/watch?v=w7lJa...eature=related
I found this video which seems to have the closest Start up noise (The other noises the car presents in the video are NOT present)

THe Check engine light came on Last Nov and that is what alerted me to the Sludge issue - A flush was done and oil changed, then at 4 months mark I had oil changed again, and a compression test done. Light has not come back on.