Tick tick tick... please help.

[mike.bmw]

I've been hearing a loud intermittent ticking noise at idle.  It increases with RPM and will fade away past 3K RPM.  Generally I hear it when I'm idling at a stop light, but as I said it's intermittent so I don't hear it all the time.  The noise is similar to two shot glasses being smacked together.  It's not injector tick as it's much louder than that.  It's very hard to pinpoint the noise as it only comes on ~30 seconds at a time.  At first I thought it was coming from the valve cover, but it seems almost louder when I'm under the car (on ramps).

Here's some more, possibly relevant information:
- '91 318is w/ 144K miles.
- Timing guides and tensioner replaced.
- New water pump.
- New injectors.
- New plugs, wires, coils.
- Complete overhaul of mess under the intake.
- Upper and lower oil pan gaskets replaced last year.
- No oil leaks!  Car doesn't burning any oil.
- Oil filter housing gasket + o-ring replaced (as well as the engine mess under the intake) within the last 10K miles.
- I've used both Rotella T6 5W-40 and Mobil 1 15W-50 oil.
- It doesn't matter if the car has sat for 3 days or I've been driving for 3 hours.  The sound will come and go regardless of the engine being cold or thoroughly warmed up.

Here's a video of the ticking sound (watch all the way through, it's intermittent): https://flic.kr/p/2gtrVQb

Here's what I've done to try to diagnose and remedy this:

- Removed valve cover and inspected everything.  There's no odd wear on the cam lobes:


- Video of chain play.  Is this normal?  https://flic.kr/p/2gxMwZ1

- Yes, the cam gears are pointy, but it's one of the cam sprockets that came pointy from the factory.  See more here: http://www.m42club.com/forum/index.php?topic=19556.0

- Dropped the lower oil pan to check for loose bolts, timing guide pieces, or a blocked sump (all checked out fine, though the upper pan gasket may be protruding slightly around the pickup path)



- Replaced the timing chain tensioner (no effect).

- Changed the oil (Mobil 1 synthetic 15W50) and added Liqui Moly Lifter Additive (no effect).

- Fuel injector cleaner + 2 fresh tanks of gas (no effect).

- BMW lifter bleeding procedure (no effect).

- Changed the oil again to a 5W40 synthetic (possibly louder after changing the oil).

- Removed the alternator and A/C belts to verify it's not pulley noise (no effect).  I did NOT remove the water pump belt as you replaced that 2 years ago so I assume it's still good.

- Verified no oil leaks are present and I am not burning any oil between changes.

I have not checked the oil pressure, though the light hasn't come on.  I do know the oil light functions because when I install a new oil filter the oil light comes on for a few seconds after initial startup.  I've read that low oil pressure or a worn oil pump can cause the lifters to tick due to lack of oil flow to the top of the head.

I'm at a loss of what the noise is.  Even with a mechanics stethoscope it's very hard to pinpoint where it's coming from.

Thanks for any input!

[monty23psk]

Sounds like lifters are sticking. Even with a bleed, if they are faulty, they will begin to stick. Odd in the video you hear it well and the it goes faint. Valves sticking could be another thing.

[mike.bmw]

Sounds like lifters are sticking. Even with a bleed, if they are faulty, they will begin to stick. Odd in the video you hear it well and the it goes faint. Valves sticking could be another thing.

Yeah, it's intermittent.  Some days ticks for 10-20 seconds, goes back to normal for a minute, then starts ticking again for 10-20 seconds, then back to normal.  Some days I don't hear it at all.  Some days it seems to happen fairly regularly.  Total crapshoot.

I have noticed that I can also hear it intermittently if I downshift and take my foot off the gas (engine braking).  So it's not limited to just happening at idle.

If it's a lifter, I believe it's just one of them.  It ticks in time with one of the injectors.  If I do end up replacing the lifters I'd do them all at the same time.

Does the amount of chain play in the other linked video seem normal?

[mike.bmw]

Small update.  After removing and reinstalling the valve cover yesterday, the tick has been significantly reduced.  I put about 25 miles on the car this morning and I didn't hear it once at idle.  Perhaps the valve cover gasket wasn't seated properly or torqued properly allowing some kind of vacuum leak?  Seems like a long shot, but the car did seem to run a bit better this morning.

Small update #2.  Came back in the afternoon.  I'll be taking the car to the shop this week.

[mike.bmw]

At the risk of jinxing myself, this may have resolved itself.  I posted about it here: https://www.r3vlimited.com/board/showpost.php?p=4991561&postcount=478

I took the car to RRT earlier in the week and gave them the list of what I've done, photos, videos, and other information. After looking at the car they called me back to the garage. The car was totally silent. No ticking. It's like my kids: angels at school, but not always the best behaved at home.

So Alex, JW, and I chatted for a bit and they sent me on my way. That was 6 days and 350 miles ago. The car has not ticked since then. The car went from ticking on a regular basis to not ticking at all. I have some theories:
- RRT fixed something in ~15 minutes that was glaringly obvious and didn't want to tell me because I'd feel like a moron.
- The thinner Rotella T6 5W40 cleaned out the oil passages and removed varnish from an offending lifter. It just took a few hundred miles to do it's work.
- The Lifter Additive, which was only run for 500 miles with the Mobil 1 15W50, may have continued to work it's way through the system after draining the M1 and filling the T6.

As of right now the engine sounds like the regular old M42 sewing machine and that makes me happy.