barijan

Hi everybody. A couple of days ago I changed oil and filter on my 1999 ML320 with almost 200k miles on it.
Just after that, random but loud lifter noises started. It's just like the usual clicking noise of lifters when cold, but louder, a rhytimic and rapid "tic, tic, tic" or "tac, tac, tac, tac" when it gets louder.

Check the video here: I've boosted the audio, so it may sound worst than it really is, you can even hear the rattle of the timing chain, but the lifter ticks (or clacks) are quite noticeable.

Before the oil change some lifting noise was heard for about 10 or 15 seconds when starting the vehicle, but only when the engine was cool, for instance, in the morning.
Now the noise comes and go... and comes back again... and goes away for a while again.
Notice how it went away at 0:42 but gradually returns at 0:50.
At this "silent" point do not confuse with the timing chain noise - a "chang-ching" noise - it's because the auto audio boosting. The lifter noises are like a rapid "tac, tac, tac, tac".

Moreover, it seems to be not related to one specific cylinder. Actually, the sound seems to fade from one cylinder and appears in other, sometimes on the left side, sometimes on the right side. It actually moves!

When driving, with the windows open I can hear it, sometimes louder, sometimes quiet, sometimes disappears at all, in cycle of 2 or 3 minutes. Yesterday it was quiet almost all the time. Today, most of time it's noisy.

Here the facts:
Oil used - Mobil Super 3000 X1, API-SN, 5W40.
New fleece oil filter installed - previous was paper, not ripped.
One 200ml bottle of Militec - I've used before on this vehicle with no side efects.
Oil is on near perfect level, just on the middle of the dipstick indicator and "i.O" on the oil checker at the instrument cluster.
Oil looks very clear on the dipstick, no sign of debris, residues or anything, just light yellow clean oil.

I'm used to do oil changes, but because of lack of a proper space for doing this, the last 3 oil changes has been done by my mechanic, retired MB's, now Indy. I respect him, but he's a bit cranky and almost deaf.
But now I've decided to do it myself again.
I don't know if, due to the high mileage he was using some thicker oil - the only thing I know it that it was Mobil - and now that I got back into the specs (I think so) maybe the thinner oil is causing this.
I'm afraid asking him about the oil used before because he's so cranky that he will tell me to shove this oil bottles you know where, just because I decided to do it myself.

Here my questions:
Could the "on specs" oil cause this in an old and worn engine because it's too thin for it?
Could the fresh detergent agents on this oil dislodged some sludge and it's intermitently clogging the lifter channels?
Should I let this oil stay for longer in order to clean the system?
I heard that Militec can be harmful to a engine with sludge, because it can harden sludge deposits.
Should I drain it all and replace oil and filter?

Any advice will be appreciated.
And HAPPY HOLIDAYS !!!

barijan

I forgot to mention that the lifter noises sounds quite normal if the engine is really cold. When I start the truck it ticks for about 10 seconds and stop, just as it was before. But reappears loud as soon the engine gets warm, doing that come-and-go cycle. That didn't use to happen before.
It's specially nasty when you restart it warm, for instance, after a 5 minute stop.
Maybe because the oil gets even thinner when hot?

The whooping sound is the fan. But it's fine. Fan clutch has been replaced recently and it engages well when hot. The engine was at operating temperature when I made the video.
But I noticed that the fan may sound "flapping" only in this video because, somehow, its sound has been "modulated" by the loud clicking noise. Maybe some characteristic of my cell phone microphone. Actually the fan sound it's a constant "whoosh" as the RPM increases.

Also, there's the timming chain noise, it has some, but not actually as loud as it sounds on the video. You barely can hear it if the hood is closed.

barijan

Hi fellas! Problem solved. Hurray!

Keeping the history short - Bad Oil.
I drained it and replaced by Mobil 1 0W-40 (MB 229.5 approved).
Now the engine is purring as before. No more lifter noises. Even the timing chain noise is less noticable.

Now the long - and funny - version of the history:
The oil was the culprit, although, my old fella, the retired MB mechanic, said that the oil I've used, per se, is not supposed to be so bad. Actually it would be aceptable. But something was very wrong with it.

He got some from the dipstick and said: -"Man, this is the crapiest stinky crap I've seen".
And then he showed me that, besides the fact it looks clear and thin, when you try to rub a drop between the tip of your fingers, it's sticky. It's still thin, but somehow gluey and tacky. A real Mobil oil never would be like this.

Then, he asked me where I've bought this stuff from. And I said, online.
His reaction was unflappable: -"You dumb ignorant idiot, don't you know these websites are full of tampered oils, made specially for fools like you. You must to buy it from reputable stores only. You thought you were saving a few bucks buying it online from nobody knows, but actually you could ruin you engine with it."

So we both changed the oil right away, leting it drain well in order to get rid of this stuff for good, and filled it up with Mobil 1 and a fresh filter.
We did the lifter filling procedure and that's it. No more noise.

As if I've not been beaten enough I dared asked him if my 200k miles engine is not worn and old for such fine oil, and he, as always with his finesse, replied:
-"Your brain may be worn and old. If you're not fool enough to put crap on it again and mantain it properly, such engine is supposed to be bulet-proof and can make a million miles!" - Just as Witek_M said, but much more politely.
As my fella is half-deaf he just shout it at loud. Oh, what embarassment!

I can't blame the Mobil Super 3000 X1 5W40 itself because it's not supposed to be a bad oil. Instead it's supposed to be fine. But something is wrong with the bottles I got online. I'll try to get my money back, since the website is a local branch of eBay and has a purchase protection program.
But the relief for having my engine back to it's good shape is good enough for now!

Lesson #1 learned: Stick to MB 229.5 only.
Lesson #2 learned: Buy from reputable sources.
Lesson #3 learned: Listen to the pro's advices on the forums.
Lesson #4 learned: Do not give cause for the wrath of my mechanic.

Thanks all and happy new year!

ricksmerc

I changed to 15w40 last year. My ml270 has 160k and the change from 10w40 to 15w40 which reduced the startup tick tick noise that was evident for a few minutes on startup.