The W124 E220 has a pronounced ticking noise, which becomes more pronounced when the vehicle is heated.

[ML350_Colin]

I own a 1995 E220 equipped with the M111 engine, which has recently had a noticeable ticking/tapping sound. The issue began in the previous fall, and I presumed it was related to one of the tappets. The problem is closely correlated with the engine's revolutions per minute and seems to originate from the upper part of the engine, namely towards the rear. During the Christmas period, I had the head gasket repaired and all the tappets were changed. However, the noise persisted despite these repairs. The engine emits a scarcely perceptible sound while it is cold, but becomes sufficiently loud when it is hot, prompting others to enquire about the car's condition.

With the current beautiful weather allowing me to drive with the windows open, I am acutely aware of the issue and want to resolve it. However, the local Mercedes expert has indicated that identifying the cause may be a time-consuming and costly endeavour. Given my reasonable proficiency in mechanical matters, what should be my first focus for investigation? A buddy has recommended that I address the issue by using a higher viscosity oil to fill the engine, since it exacerbates when exposed to high temperatures.

Seeking guidance and suggestions

[bvlenci]

It is possible that the issue might be caused by a valve. There may be a little issue with the connection between the connecting rod and the piston gudgeon pin. As your expert said, it is difficult to establish the issue without dismantling the engine, which would incur expenditures similar to replacing it with a reliable used motor. Using a thicker oil may be used as a diagnostic tool to determine whether excessive clearance, wear, or bearing issues are present, since it has the potential to reduce noise levels. At the very least, this will provide you with a more accurate understanding of the geographical area you are now situated in.

It seems that there may be an uncommon issue with the exhaust manifold, such as a fracture or leak, which might potentially cause an odd sound.

[Rojoires]

Take a look at my thread documenting the process of restoring a 124.

[ML350_Colin]

Thank you for the prompt responses, gentlemen.

Regarding the valves, what may be the origin of the tapping noise they produce? I pondered if the issue was connected to the exhaust, but the noise does not seem to originate from either the exhaust or the heat shields (I own a mechanic's stethoscope to investigate).

Bruce - I have thoroughly perused your post (a really astonishing streak of unfortunate events you have experienced - hoping for a turn of events in a positive direction!). Are you implying that the tapping sounds I am hearing might be indicative of a worn-out crankshaft bearing, subtly indicating that my engine is at risk of imminent self-destruction?

[Rojoires]

I trust that I am not the harbinger of catastrophe.

Identifying the source of tapping or banging noises may be somewhat challenging. The sound in my automobile originated from the front top end and travelled to the back bottom end.

Any factor that has a positive correlation with engine speed when the vehicle is not in motion should be thoroughly examined.

I am unable to provide any words of solace. Apologies. Elevate the object and use a mechanics stethoscope to examine it. This may indicate the location of the knock.

Best wishes.

[SkippyTom]

The most probable cause is a malfunctioning or jammed hydraulic tappet, which is then likely to be accompanied by camshaft attrition.
The valve train noise occurs while the engine is running at half its speed, whereas the noise from the bottom end (piston/rod/crank) occurs when the engine is running at its maximum speed.

[AMG33D]

However, locating unusual sounds, particularly those sent via the internet, may be exasperating. Cracked exhaust manifolds, caused by a broken stud or other issues, may lead to a ticking noise that becomes more pronounced as the engine heats up. Engine revolutions per minute (RPM)

I had identical symptoms on my last s123 vehicle equipped with the m102 engine. The reason of the issue was a fractured manifold bolt in my situation. However, without using a stethoscope or doing a thorough examination, the noise was comparable to a severe rattling originating from the upper part of the engine. The prevalence of broken exhaust manifolds on the M111 engine is uncertain, although they are certainly not uncommon.

[bvlenci]

THIS SUGGESTS THE LOCATION OF THE CRACK - the one seen in the photo has been poorly welded.

[EatSuru]

By removing the oil filler cap, you may determine if the noise is originating from within or outside the source.

[ML350_Colin]

Observing the frequency of the ticks seems to align well with one-fourth of the engine's revolutions per minute, indicating that issues related to valves and similar components may be excluded as potential causes.

However, when I opened the oil cap while the engine was running, I did not hear any noise coming from within the engine, just a faint humming sound, which I presume is the noise produced by the valve train as it operates during hundreds of explosions every minute.

Over the weekend, I want to carefully examine the exhaust system.

Thank you for the ideas, they are really appreciated.

Greetings