Not being there and seeing the whole thing with the noise is a bit of a disadvantage, but I'll say this, I would not run that engine anymore!
To me, that sounds like an internal noise and serious at that. Something is loose somewhere. Bad connecting rod or something in the valve train.
When you changed the oil, what did it look like? Anything that resembled metallic glitter in the oil or even pieces of metal?
I'd first peel off that valve cover and look at the valve train.

I gotta say it.
You need to find a different mechanic ASAP. Anybody that says the alternator and tensioner are the cause of that noise, hasn't a clue.
You should find that mechanic, rip the wrench out of hands and hit him upside the head with it and tell him your welcome. Sheesh.

 

Thanks for the reply and questions, AndreasPassat! I didn't notice anything off with the oil when I changed it--metallic glitter or shavings of any kind. Your comment about something being loose makes sense to me as it sounds like that to me too. Regarding pulling the valve cover as you recommend to have a look around, I have a question: would I need to replace the gasket when I put it back together? I replaced that gasket a few years ago but can't remember if pulling the valve cover damages the gasket.

I am pretty surprised too by the local German shop saying this was the alternator and charging me over a $100 to tell me that! I don't know much about engines, but the more I think about it, it just doesn't make sense! They are a reputable shop too!

I'll pull the valve cover and see what I find. Might be a few days before I can get to it, so stay tuned.

Thanks again!

 

I agree, it sounds like something bouncing around under the valve cover. I would also pull the timing belt covers if you can't find anything wrong under the valve cover. You can try a mechanic's stethoscope (or a screw driver to your ear) to pinpoint the noise.

 

Ha, I thought of that also, that is a pretty solid clunking noise though. Can't imagine what's flopping around by the cams to make that kind of noise. The frequency of the noise seems like it could be related to the timing because of how slow it's spinning at idle.
To me, that almost sounds like a rod/crank bearing that is gone or a thrust washer that has slipped out of place. Eerily similar to a completely worn out set of crankshaft bearings I had on one of my previous cars.
Obviously only speculation at this point.

 

Pull the timing belt cover at the front first. You can run the engine with the top timing belt cover removed. Unless it is a new gasket (like only months old), then I would replace the valve cover gasket if removing it. No, you should not run the engine with the valve cover removed. Oil will get everywhere.

 

I would first check the timing belt tensioner pulley bearing. ( And that is not far from the mechanics diagnosis)

 

Finally getting a chance to update you all on the situation with my Passat and that engine noise. After hearing your thoughts about the valve train and talking to a friend on the phone who has worked on this car before, I did the screwdriver sound test with the longest one I had (mentioned by PZ) and narrowed it down to two places. (see attached image with the valve cover on and two red circles). The part of the engine where the engine code is etched on is where the sound was the loudest. After talking to this friend (a mechanic), we thought it might be the VVT actuator and so I replaced it. Bit of a bear to get the old part out and ended up needing to buy an aluminum VVT compression tool online from 034 Motor Sports (I somehow broke the plastic one that came with the new part as many people seem to do) to complete the job. Took days as a result. Got it all back together yesterday and took it for a spin to make sure the timing hadn't somehow been altered (I checked and rechecked this before putting everything back together). Drove fine; no dash lights, etc... and the noise is exactly the same as before. 😔

So, I am back to square one. The cams looked fine when I was in there. The cam chain looked fine. The engine is pretty discolored, but imagine oil can do that over the years. Seemed a little dirty as well. I replaced the valve cover gasket as VAGguy recommended as well. Oh... found that someone had stripped the head of one of the cam seal retainer bolts previously and it would not allow me to unscrew it. Probably whoever did the timing belt the last time. Why would they (a shop) use this bolt if they damaged the head! Had to drive to the local Audi dealer (25 minutes away) to get a few new bolts just to be on the safe side. Getting that damaged bolt out was... stressful! Accidentally broke the tip of the extractor off in the bolt! Long story.

Next place seems to be the timing belt area as Tomvw mentioned. I am at a point where throwing parts at this doesn't seem to be logical anymore. The timing belt was last replaced in 2016 and not even 30,000 miles ago. Belt looked fine when I took the cover off. Hard to see much down there as the space is very narrow.

I'll add a few pictures to give a look at the engine. Noticed that cylinder 1 and 4 were wet looking under the spark plugs and the plugs themselves were a bit corroded. Ideas? Cylinder 2 and 3 were dry/seemed free from carbon buildup. Is the discoloration of the valve/cam area normal from the engine oil?

I await your feedback and thoughts. And thank you all for chiming in so quickly and honestly! This is my first time in a forum; I can see why they exist!

 

Watched the video again.

I had roughly that same sound and frequency in an ATW 1.8T Passat I had a while back. It was a an extra car, so I never really looked into it much. It eventually went away without any intervention.

Under that valve cover looks a little cruddy. This is mine after 176k hard miles on 5w40 synthetic since new at 5k intervals.

Did you put the old plugs back in or replace them?
Manual or auto trans? Mine was manual.

 

Watched the video again.

I had roughly that same sound and frequency in an ATW 1.8T Passat I had a while back. It was a an extra car, so I never really looked into it much. It eventually went away without any intervention.

Under that valve cover looks a little cruddy. This is mine after 176k hard miles on 5w40 synthetic since new at 5k intervals.

View attachment 103357
Did you put the old plugs back in or replace them?
Manual or auto trans? Mine was manual.

Your engine looks quite a bit cleaner than mine! I was a little surprised to see so much grit in my engine, especially on the exhaust cam side. Mine is much more stained. I had an oil sludge issue with this car many years ago (very expensive to have fixed) and that might be reflected in the color of my engine being stained so much and being so gritty. The under side of the valve cover was really bad as well--cleaned it as best I could.

I put the old plugs back in for now but will plan to change them out when I figure out what this noise is. They are really spendy as well! It's an automatic transmission. I have had the fluid changed twice during ownership (I know they say it supposed to be lifetime fluid, but I have heard from others that it is a good idea to change it to prolong the transmission's life--too expensive to replace!). I love the automatic trans, but hope it continues to last.

Just curious... that sound in your other car's engine: did it get stronger over time before it resolved itself? And any memory of how long before it resolved itself?

 

I suggest you don't run it again until you have checked the timing belt roller bearings.
If a Tb roller bearing is making that noise, I would expect bent valves or worse very soon.

 

Thanks, Tomvw! I'll try to do a screwdriver test to see if I can isolate the sound to the timing parts/roller bearing. It's sitting in the garage and I am driving my wife's car for now. Just wondering if the intermittent/non rhythmic nature of the sound and only coming on when warm fits with the more rhythmic nature I would expect from the timing parts? Nothing about this sound makes sense to me, but I guess that shouldn't be too much of a surprise as I have a lot to learn about cars/engines and how things all work together. Thanks for the recommendation. I'll let you know what I find. If it is the roller bearing, would you recommend just doing a whole timing belt component change rather than just that one part? It was last done in 2016 and about 27,000 miles ago.
Now that I am thinking... the belt seemed to be slightly forward of the teeth on the exhaust cam wheel; just slightly but it caught my attention. Hmmm...

 

As far as I can tell from the video, that noise is consistent with a bearing about to seize and/or fly apart.
I suggest you at least do a visual check of the TB roller bearings before starting or cranking the engine again.

 

Thanks for the suggestion, Tomvw. I pulled the TB cover and checked the tensioner pulley bearing and did a stethoscope test. Normal noise there. Nothing matching the knocking sound. I have been driving this car since then (about the last 1.5 months) and nothing has changed. Considering to pull the front clip off and replace the whole TB system/waterpump, but not really excited to do that if it isn't the problem.

 

It's probably not the case here, but the water pump in my AWM made sounds similar to that as it was going out.

I know you changed it just a few miles ago, but try your stethoscope screwdriver closer to the water pump just in case.

 

It's probably not the case here, but the water pump in my AWM made sounds similar to that as it was going out.

I know you changed it just a few miles ago, but try your stethoscope screwdriver closer to the water pump just in case.

FamousDan -- I can hear the knocking sound at the water pump with a stethoscope but I can also hear it almost just as well to the right on the drivers side of the block. The sound seems to radiate. I can even hear it in the EGR valve, though not quite as strong. How long did your water pump last before it failed? I have had this sound for months and still drive the car every week.

 

If it's noisiest at the front, I would pull the alternator belt and a/c belt and see if the noise stops. If not, I would remove the timing belt covers and check the water pump and tension damper pulleys. Have you checked the oil pressure?

 

PZ -- that is a good idea. Checked the TB tensioner and water pump and can hear the knock at the water pump but also in other places. Have not checked the oil pressure other than the gauge on the dash and it is always the same. No dips that I can tell. Not sure how to check the oil pressure manually.

 

There is a brass plug in the oil filter bracket. Remove that and plug in a mechanical gauge. Some parts stores rent them for free with a deposit. I bought one years ago from Harbor Freight and I have checked several cars with it.

 

Thanks, PZ! I learned something new today, thanks to you!

 

Have you removed the belts and checked if the noise stopped?
Since it's non-rhythmic, I would rule out an internal engine problem. It does sound like a bad bearing, maybe the water pump, but could just as easily be the belt driven fan bearing, which is just below the alternator. They usually whine when they go bad.

 

I changed one on a 2.7T that had a small coolant leak for several weeks. The last week it got worse, so he drove it the 6 miles to my house. When I pulled it apart, I found the pump had seized and had just started burning through the belt and turning the pulley blue from heat. Luckily, it did not skip time and survived. I've heard several water pumps and bearings fail and they can sound similar.

 

Most of you who have helped me with perspectives on this thread probably have wondered what happened with that engine knocking sound! Well, here is what I can share with you:
The sound switched to really bad one day and I limped the car home and parked it. It sounded like engine death! I ordered a Gates timing belt/water pump kit and after reading several posts on PW, I started the project. Before pulling the timing belt components, a friend advised me to run the engine without the serpentine and AC belts. Same sound, so I knew it was not either the AC pump or the power steering pump. When I pulled the old water pump off, it was corroded of course, but also the shaft was not straight and there was a little play in it. That would explain why the water pump spindle seemed to move in a more oval motion than round. I have attached a pic of the old water pump. Put everything back together (new timing parts) and double checked the timing (ok, I checked the marks multiple times to be safe) and started it up... no more engine death sound! Problem solved! The noise a bad bearing can make is unreal! Put the whole front of the car back together and it sounded... normal. No nocks or clangs. For all the work I did, I almost expected to be able to feel something stronger or better, but all I got was no more noise. In the end, I'm ok with that.
About a month and a half later the top camshaft seal started leaking oil really bad. Just replaced that last night and so far all seems to be well on the engine front. I also changed the transmission (AT) fluid and filter (used almost 6 liters of Liquimoly Top Tech 1200 ATF) after reading some very helpful reviews here. No shavings in the pan or on the magnets. But shifting doesn't seem to be any better than before, if not a little worse. I can hear the trans spinning up louder than before too. Might have to start a new thread on that one.
The support you all have given me and narrowing in on the water pump was invaluable!
Just wanted to close the loop and say thank you to everyone!

 

It's good to see that you have solved that problem.