Hello! Pleasure to meet you all and thanks for checking out my thread.

My 99 e320 is running flawlessly, haven't had a dash light or issue aside from oil changes for a couple years. Holds a steady idle and was just considering doing motor mounts.

Until I noticed this noise:

https://youtu.be/5xNU_h6itbs

It is very noticeable with the cover off the motor and I can't quite pin down what it is with my mechanic's stethoscope. I've seen many threads with identical sound clips but didn't see any exact conclusion on what causes it.

I've read speculation that it's timing chain, tensioner, oil pump, lifters, that is is an emergency, it's good for 50k miles, etc. Please help me narrow the list.

I can't say what it is.
But you can rule out the individual pulleys like the tension pulley by getting some WD-40 or some 3 in 1 oil in a spray can with the straw. Carefully and sparingly spray the pulley between the belt and the motor. basically you are trying to lube the bearing.Don't get this stuff on your belt as it will degrade the belt, shorten it's life and leave gunk on your pulleys.
If you have lifter noise I recommend adding 1/2 a quart of Mystery oil to your engine oil. This has reduced lifter noise in many of my cars.

Good idea! My plan tonight is actually to give it a quick start without the belt on at all to make sure it's not the timing chain

I had a recent experience with a timing chain defect (stiff link) and the symptom was a cyclical/periodic noise with a repetition rate about 1Hz. Yours seems to have that repetition rate also. That is about the time it takes for the chain to go around once at idle. There is nothing else on the engine that revolves at that speed (at least not on my engine). Do take the belt off to make sure.

In my case I had to change the chain. Mine is a M111.

Good luck

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Unfortunately I took off the serp belt and ran the motor only to still hear the noise. It sounds almost absolutely like it's coming from the area around the thing that makes the vacuum noise for 90 seconds after starting the car, but the trusty mechanic's stethoscope proves that doesn't make any similar noise.

If it is the timing chain, what are my options aside from replacing it? I was just on the edge of contemplating replacing this car with an e55 actually. If it will go for another 25-50k miles then I'll just deal with the noise.

It's a shame I can't guarantee that a new chain tensioner would fix it, that part looks to be about 50-60$.

Sorry I am no expert on that. If it was a M111 then at least I could speak from experience. I suppose you could try the tensioner. My guess is that won't help but maybe someone else has a different opinion. I could be wrong.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

good job on the video, certainly sounds chain-like to my ear. If only there were a way to spy inside there?

I suppose it wouldn't be a bad idea to put some new valve cover gaskets on and take a peek, but I won't have access to my dad's shop until this weekend so it will have to at least wait till then.

In the meantime, I noticed that the noise is present and identical when the motor is totally cold and hot. Maybe the tensioner has totally given out?

If I hover the TPS at around 750 rpm, I can hear the sound change to a more steady version (but definitely there) that is more or less hidden by the increased regular motor noise.

If it's the timing chain, my guess is that it's a light graze on the top driver's side guard

Im assuming your tensioner is the same as on the M104 engine, a ratcheting plunger pushed by a spring so that it clicks against a notch as wear occurs. Forward but not back. Now on taking my heads off and doing the RR work I found the tensioner will easily stick on the notches and when you install it must be backed off and then you take a small ratchet drive or bolt and click click..push it forward to contact the chain. Not hard, but firmly. Mine turned out great but you hear merz' all the time with clanky buzzing sewing machine sounding timing chains like my previous E320, they smooth out when the engine warms up. I suspect timing chain wear with a stuck tensioner. My chain was VERY worn but no noises BC the tensioner works well. Even some flat spots on the chain shoulders. 200K miles and likely original chain. Then you've also got the issue of those balancer shafts and other harmonics going on in those V engines..

Hmm driver's side guard..and the support bolts for that and your stethoscope?? I used to use an old phonograph pickup and a transistor radio which made an electronic listening device to keep track of my old VW's tappets. Forgot all about that! Worked great!

Good luck.

I think they may have actually removed the ratcheting feature of the m112 chain tensioner, leading me to believe that it may just be providing sub par pressure.

It sounds like it's coming from exactly where the thermostat is by ear, but nothing makes a similar noise over the stethoscope

I don't have much experience with chain issues.
But I do remember that my dad's 300SDL ran a little funny toward the end because the chain had stretched after 250,000 miles. it needed a new chain, but he ran it like that so long that the gear teeth had ground down and fit the chain. So, it was a moot issue. He drove it like that for another 75,000 miles or so.

I mean I keep hearing that it's very unlikely to be my chain at 150k miles, but I just don't know what else it could be in that area!

Mine didn't act up until 325K.

I keep hearing about how the chain shouldn't be an area of wear at 150k. I just ordered a new tensioner so toss one back in hopes that it works!

Before changing your tensioner maybe you should pinpoint the problem.
I'm not a mechanic so I figure that anytime I change a part there is at least a 25% chance I will make it worse.

Have you tried adding Mystery Oil?
Can anyone second this recommendation?


I've never worked on a timing chain, but can you inspect it?
Could you manually rotate it by say turning the main pulley? You might see a wonky link.