anavabi

Hi Everyone,
On my ML500 I started having tapping noise when engine is cold and under load. It seems to be coming from the valves.Tapping noise happens when engine is revved up either at idle or during driving. No noise when stopped. All this happens when engine is still warming up. Once engine is warmed up, all the noise goes away.
Your insight and thought will be much appreciated.
Thanks,

Maj. Dundee

I have the same exact problem which is a valve lifter noise. Start cold eng. and immediately shift to D and then back to P & see if the noise diminishes greatly.

This reduces the cold idle speed.

anavabi

Thanks for the response. Is there a remedy? Any additives?

kombifan

Try this kit.

https://www.fcpeuro.com/products/8-c...i-moly-lmk0005

Maj. Dundee

Did you do as I did? Shifting from P to D and then P?

SunnyT

Maj is right. It's most likely lifter noise. Mine did that too. It's to do with oil deposits building up in the tiny oil flow holes the lifters have. Old oil will gunk that up and they struggle to get enough oil to run silently. An annoyance of the M113 engine design. Not to worry though, a good deep clean can fix that.

Good kit, but you should add two Liqui Moly 20004 Hydraulic Lifter Additive bottles to the list. Just copy paste that into Amazon.

The kit gives you two Engine Flush bottles, enough to treat 10L of oil. Take advantage of that by doing a double oil change flush.

1. Start with the first Engine Flush bottle (1 per 5L of oil). Run it for a solid 20min with the car in idle to warm up the oil and really cycle the product. They say 13min, but that won't be enough to hit the temp you want in idle. It won't damage anything as long as you DO NOT DRIVE OR REV
2. Flush it all out and let it drip for a while. Get as much as possible out
3. Fill oil as usual with something synthetic, but cheap. You'll be draining this oil in a couple minutes anyway
4. Pour the second Engine Flush into it and run it again. This time 10-15min
5. Flush that gunk out of that engine. Even though the oil is new you should see more old deposits pour out
6. After the two flushes pour ONE quart of high quality synthetic oil in
7. Add all the additives (shake them all well)
8. Fill up with the rest of the oil. Adding the additives before the rest of the oil will help mix them in the pan
9. Change filter, seals, etc.
10. Boom, smooth as butter

I had this issue in the past, but after sticking to a regular Liqui Moly flush and additive routine it is now ridiculously quiet. If you do the above steps like I did, your noises should be gone. Keep in mind it is not a permanent fix as this is an engine design thing and over time the more oil gets gunked in those tiny holes the louder the lifters will get again. It's just something you'll have to add once a year or so. Depends on your usage and oil changes.

anavabi

I'm not that lucky! Mind you it wasn't that "cold" an engine at the time. I'll try tomorrow again and let you know.

anavabi

Thank you for your guidance.

anavabi

After all my luck's not that bad. I did turn to D and P quickly, and it somehow magically stopped the tapping noise. What was that!

SunnyT

That was you lowering the RPMs by aborting the car's programmed "cat warm up" or whatever term you want to give it. I'm sure as soon as you accelerate the noise comes back because the increased oil pressure cannot adequately lubricate the lifters in its thick state yet.

Let me try and visualize how small these holes are and why they can clog so easily.

This is a lifter

It's that small! Look how tiny those oil feed holes are.


Now, most commonly these just get a little clogged and a flush solves the issue. Neglect it and starving them of oil can cause the spring mechanism to go bad and break it entirely. Lots of labor hours (a.k.a $$$$) to get that fixed. The other issue might be that the oil tube is broken/clogged, which is the connecting bit that delivers oil to both sides. So, three things can be the cause. Clogged hole, bad lifter, bad oil tube.

Doing the flush is great maintenance and eliminates one of the choices in what can cause the noise. Might even improve other things in your engine with the additives.
Either way, the cost of the oil and additives is much cheaper than what a shop will run you to take apart your engine, remove the cams, secure the timing chains, depressurize all the lifters, find the broken one/ones, replace it, re-pressurize them, put it all back together, refill whatever oil was lost and hope they didn't forget anything.

If you want more detailed information about lifter noise just Google "M113 lifter noise" and you will see some very detailed results from a bunch of Mercedes forums and even videos of garages taking the block apart to explain how they work and why they can go bad. Quite entertaining if you're into mechanics and want to see the pretty internals of your engine.


These cars last forever when living by the mantra "an ounce of prevention is worth a pound of cure"
In the end I can't tell you what to do. I can only suggest advice based on my experience and knowledge. What you do with it is up to you. Hope it works out well.

anavabi

But why does the tapping stop after initial engine warm up

SunnyT

The hotter oil gets the thinner it is. When you are cooking and put olive oil in the pan trying to spread it in the beginning when it’s cold is hard, but once it’s warm it easily spreads around the entire pan. This is because oil turns thinner/“more liquid” with heat. The thinner (hot) oil slips through small spaces a lot easier than thick (cold) oil.

Which is why in winter people use a different grade oil than in summer, but that is an entirely different story and many threads exist with a lot of detail on the subject. The power of viscosity!

kombifan

Amnvi, sunny t knows what he's talking about


I also had loud lifter noise, and after using th e kit I posted it quieted down extremely.
The engine flush paired with the ceratec does wonders for your engine.
I also prefer using the Liqui molly 229.5 oil as imo it is better for the engine.