2010A8Lsport

Is there any way that an excessive crankcase vacuum situation could cause any kind of top end ticking? Could it affect oil pressure?

Im trying to sort out my mystery tick which seems to be localized at the valve covers/intake manifold.

MP4.2+6.0

4.2's often have some ticking. Some do, some don't. Search on it (via Google) for a variety of stories, deep and shallow dives, and so on.

First suggestion is oil flush/cleaner right before next oil change--the pour it in the crankcase stuff. Obviously easy to try and see if any benefit.

After that, dive into the search/posts on the (oil) antidrainback valve, including ones where I replied. Deeper dive if you want to try there--under the intake manifold in the V area so takes some disassembly to get at.

2010A8Lsport

I've already done an engine flush and refill with 502 spec 5w40. I considered the anti drainback valves but if they were malfunctioning I would have a worse rattle at startup and it's always tick free from a cold start.

Im going to get the oil separator cleaned out and replace the diaphragm with a new one. See if that clears up the high vacuum situation and also see if that affects the ticking noise. I may still swap out all of the lifters and rockers but I'll take it one step at a time. Diaphragm is already on order.

Thank you for the input MP4.2

MP4.2+6.0

My own experience is antidrainback issues can be all over the map. Not a well documented part of the motor. I know about them from the 2.8 12V V6 back to 1996. There when they got weird you could get a squeal like literally a cat in the worst heat ever. Happened hot and sounded normal until the moment it went wild. Had it happen/heard it first person, and sure enough it was those drain valves when we replaced them. There was a TSB on it back when they were in paper form. In D4 they are probably now ground zero for the 4.0T turbo meltdowns, though Audi isn't talking directly, and it isn't noise related. Remember, any multi vis oil thickens as it gets hot, so it it may have more difficulty clearing any fine screens and then come up short on flow. The flow issue is the apparent D4 turbo one, where with some clogging of the screens the downstream turbo bearings in the oil circuit then seem to get oil starved and fry.

Rather than speculate, localize noise better. Use an automotive stethoscope. Or poor man's version I use--really big/long bladed screwdriver with plastic end to ear and tip against metal. Works very well. Just start touching it all around motor and suspect areas. Don't exclude drivetrain auxiliaries, pulleys, etc., either, which can have only vague locational clues until you do that sound detection test.

2010A8Lsport

I have an automotive stethoscope and I've tried tracing out the noise and the only noisy part I have found comes from the plastic intake manifold... the tick sounds way too metallic for an all plastic intake though. I feel that if it's a mechanical issue it likely wouldn't be silent for the first minute from a cold start? Do you know exactly what the oil path flow I should go and from the anti drain back valves, could they starve the top end of oil in any way?

MP4.2+6.0

So, I think you are well beyond any available practical info around on the 4.2, at least that I've come upon. Yet more so on the FSI flavor, which is newer and not yet wrenched on as much, and probably lower volume in at least the D3 type design. Even on the board here, I would say the level of experience and knowledge on just D3 4.2 flavors is probably 10x or more on the port design relative to FSI. Again, your best comparable ones are Q7 Gen 1 and C6 4.2. Not sure about the 4.2 S4's and S5's, which at least had some cam chain drive differences IIRC. Meanwhile there are probably 20-20x more C6 and Q7 4.2's sold relative to D3 FSI 4.2, maybe 50x. You might try some deep searches there. Other suggestion is track down the 4.2FSI SSP and look at the text and diagrams around the oil circulation system as well as the fine oil separator. The diagrams won't get into all the specific parts and passages though. I think you may find there are some elements of that fine oil separation set up that also have some noise control aspects. Finally, I am sort of recalling the newer designs have an oil pressure related tweak that increases fuel economy by reducing unnecessarily high oil pressure. If that is valved and malfunctioning, I suppose that could be an issue somehow leading to a flow issue under certain conditions. But no specific knowledge on how it is set up, parts locations, design parameters, etc. Might be in the full manual documentation via ErWin too.

2010A8Lsport

Thank you for the insight. I am beginning to think you are on the right track regarding the oil anti-drainback valves. I am thinking there may be something in the passage leading up to them that draws up and blocks them once the oil pressure comes up and thus choking off proper pressure to the top end of the motor. It could explain why I have no ticking noises on initial cold startup and then it develops shortly after. I will dive in deeper and take a look at them and report back.