96 Passat knocking at idle

I could really use some seasoned advice - I am new to the world of diesel.

I purchased my inlaws 96 Passat TDI after my nephew ran with the moderate oil pressure (not zero, the other one) warning on for a half mile or so. I decided to drop the pan, clean out the goop in the pan, replace the oil pump, and check the main and rod bearings. I anticipated 195,000 miles of gunk on the internals, as the externals were...filthy.

Much to my surprise, the pan was spotless, the pickup tube on the oil pump completely clear. Remarkably clean. Hmmmm. I plastigaged the mains and rods and found them all within wear limits, and nothing alarming in their appearance. I changed out the rod bearings and the mains that i could reach, plastigaging as I went, and all seemed great. Not a scratch on any crank journal. I put the new pump in, and when I barred the engine over to check rotation for priming the oil pump, I discovered the auxilliary shaft wasn't turning. A used pulley, some loctite and a new woodruff key, and my oil pressure came right up when I started priming.

The inside of the valve cover was spotless as well, no signs of camshaft damage. I was very optimistic at this point.

I got it back together and after much cleaning and replacing fuel return lines and such, it fired right up and sounded great. 100 psi oil pressure, dropped down after awhile to the 40's. All seemed well.

2000 miles later, I have a "Tack,tack,tack,tack...." sound when the engine comes up to temperature, at idle. Driving it about, it sounds great. No driveability issues, starts easily, great performance, plenty of boost.

So I begin to worry, wonder and investigate....oil pressure starts at 100psi at start but drops directly proportionally with coolant temperature. At operating temperature I have 18 to 23 psi, which goes back up linearly with engine RPM to 80+ psi.

I checked injection timing and the value it was asking for and actual are within 0.2 deg, and nowhere near 2 deg BTCD, just a few tenths ATDC as its calling for.

I opened the valve cover hot, put cam assembly lube on the lobes and fired it back up - no change.

Today I dropped the pan - I feel zero play on any connecting rod (aside from thrust). I popped the #1 and #4 rod caps off to have a look. The cap side bearings were a little scuffed but fairly normal looking. The rod sides are much more heavily worn. I have pix if anyone wishes to see, but my gut is telling me I'm barking up the wrong tree.

I welcome suggestions, torque recommendations on the rod bolts, sympathy and advice. What should I do next?

How do the lifters look? You'd have to remove the cam to get a real good look at them. At that point, I'd just replace them while you're in there.

I saw no evidence of galling, the lifters not being pressed on by the cam rotated freely, but I didn't realize they were hydraulic. I was thinking they were like the cam followers on Ferrari/Fiat OHC's. I'll order a set, as I realized this morning I'll need new rod bolts anyway. This time, no cheap con rod bearings either. I should replace the cam seal, any other suggestions while I have the cam out?

When the wife ran my ALH on low pressure, it made a knocking sound as well. I swore up and down that it sounded like a rod knock. It wasn't. It was the combination of a collapsed lifter (several actually) and bad scarring on the cam journals. The cam tower on the passenger side of the engine is the last moving part to receive lubrication and it's usually one of the first things to go. (that and the turbo). If lubrication was lost even for 60 seconds, that journal is probably trashed. I highly recommend you pull the cam and have a look. The bottom end is probably just fine. I can tell you that if the journals are scarred, better shop around for a new head (~$1,000 for Kolbenschmidt). If the journals look fine, I'd look at the lifters with a magnifying glass. Check for any cracks or signs of excessive wear. Check for signs of excessive wear in the lifter bores on the head. With 195k, there will be bore wear at 6 and 12 relative to looking the engine from the front. If all that checks out, I would then pull the rod caps and examine each rod bearing. If there truly is rod knock, the bearings will be damaged. If that looks good, pull the main bearings. All of that can be done without removing the engine.

Sorry man, you've got a big project ahead.

If you find the head does need replacement, send it to member Franko6; he can do a lot of magic on these heads. See the "cyl head repair" link in my singature for examples and contact info.

Tony

You should not waste time to find the source of this knock when it is not causing any drivability problems. Think of this as another inherent diesel engine noise. Don't waste time to disassable the engine when you are not experiencing any visible problems like smoking, overheating, excessive oil consumption, etc.

Did you replace the rod bolts? They are stretch bolts and require replacement.
I vote for replacing the rod bearings, bolts and install new lifters.

I'll check the torque specs for the rod bolts later this evening. IIRC the G60 rod bolts are 44lb and then 180* or is that the flywheel bolts. let me check...buy a manual if you can locate one.

Dodoma said:

You should not waste time to find the source of this knock when it is not causing any drivability problems. Think of this as another inherent diesel engine noise. Don't waste time to disassable the engine when you are not experiencing any visible problems like smoking, overheating, excessive oil consumption, etc.

Click to expand...

Seriously? Do you want to see what running a TDI for 1/2 mile without oil does?



That's what happened to my car driving from a cold start to about 10 blocks away with the oil light on. Completely DESTROYED the head, lifters and turbo. That was with my wife driving who has arguably never floored it or taken the car over 65 in her life. Whenever there is unusual noise, you should always do your due diligence and check parts before you end up buying a whole new engine instead of just a head or something.

Terrible advice.

Oh my sweet word!!! Now I'm going to have nightmares...thanks.

New lifters...still noisy....hmm.

I installed a new set of lifters, none of the originals looked unhappy at all, but a set of nice german lifters is a small price to pay.

No galling, no unusual wear on the cam, although I did NOT extract it from the head. My fingernail couldn't detect even the tiniest scratch.

I used new rod bolts, even own and use a degree indicator to make sure I went 90.000 degrees after hitting spec. Installed Calico coated rod bearings for an extra measure of happiness. I'm a big fan of babbitted bearings, and these coating should exceed them in performance.

I'm going to drive it for a bit and see if I see any change, start saving for a teardown at some point.

I'll post pictures next time I'm inside the valve cover. Meanwhile, thank you to everyone for the kind assistance.

Mine was making some funky sounds awhile back and it was the serpentine belt tensioner. Don't overlook that! Sounds like your oiling system is in good shape. Also when my aux shaft came loose and the oil pressure light came on, I thought My bottom end was toast but inspection revealed nothing. A new oil pump and aux shaft(plenty of loc tite on the driver bolt) and I'm 25k closer to 400K!

Cam and lifters should always be replaced as a set.

have you cracked each injector nut, one at a time, to see if the noise goes away when you "de-fuel" each cylinder?

turbos10 said:

Cam and lifters should always be replaced as a set.

Click to expand...

Some guru's on here would disagree with you.

Update: 100k miles with no issues until the timing belt failed. I fear all
is lost, but perhaps y'all might need parts or a project.