The 2008 E350 vehicle has a banging sound while idling at warm temperatures, namely between 2000rpm.

[dramarena]

Greetings, everybody.
I have been encountering a noise issue in my M272 3.5 engine with 106,000 miles (which has an updated balancing shaft, so that can be ruled out as the cause).
The noise resembles a dual knocking sound emanating from a heated engine, which is seldom heard during a cold start.
The engine first operates at idle speed and gradually increases to 2000rpm. It is uncertain if this increase in loudness is accompanied by the disappearance or overshadowing of other sounds produced by the engine.
The engine operates optimally, particularly after a thorough cleaning of the intake manifold and the removal of carbon deposits from the combustion chambers using a piston soak suction method, together with manual rotation using the hand and starting motor. The Pistons were seeing a significant accumulation of carbon deposits.
Subsequently, I proceeded to cleanse the crankcase many times using new oil and liquid Moly engine flush. Then, I repeated the process with fresh oil and ATF in the crankcase. I am now using the 5W40 X-Cess motor oil and GAT nano ceramic in my automobile.
Thus far, I have covered a distance of around 300 miles after using Octan booster and Royal Purple full fuel system cleanse.
Although I have conducted extensive research, I have discovered that many individuals have reported encountering a pounding noise. However, there is currently no definitive cure or diagnostic that specifically addresses this problem.
My main concern is if this issue will escalate into a more significant problem or whether it will remain as it is and the engine will continue to function properly.
I am embarking on a lengthy journey spanning 1000 miles and I am contemplating whether or not to go with it. If I do decide to go, I would appreciate any suggestions you may have about preparations prior to doing this trip.
Thank you for your exceptional patience in reading up to this point 🙏

[veinedpanty]

Has this phenomenon evolved gradually or did it manifest abruptly? Is it exhibiting a gradual deterioration or has it been unchanged for a considerable period of time? From which part of the engine is the sound originating?
Regrettably, I am unable to provide much assistance without a minimum amount of further information. A sudden knock is always unwelcome, and I would not go from the town without first ascertaining its nature.

[dramarena]

Unexpectedly, the automobile was little used when it occurred.
The condition first deteriorated somewhat, then stabilized at the same level, with intermittent periods of disappearance lasting a few minutes.
The source is originating from bank 1 mid/from.
I heard it before at bank 2.
There have been reports of individuals driving with this banging sound for a distance of up to 70,000 miles.
Personally, I am unable to just disregard it.

[Kix]

If the cylinders are indeed heavily carboned up, the possible cause of the noise you are hearing might be piston slap resulting from rings that are stuck. Was this automobile subjected to traffic congestion during the period between oil changes at 10,000 miles? I would remove the valve covers to check for any substantial accumulation of sludge.

Do fault codes exist for large knock counts?

[dramarena]

The previous owner did not use it much and would only start it sometimes, allowing it to idle for about 15 minutes at a time.
I inspected the valve cover and saw that it seemed to be in a pristine condition. Removing carbon deposits from the top of pistons may result in leakage onto the rings, leading to their sticking. Despite my efforts to clean them using oil additives, the issue persisted.
No signs of cylinder wall scoring were seen during poroscope examination.
The car does not have any diagnostic trouble codes.

[veinedpanty]

Is it possible that the sound you are hearing is caused by an exhaust leak? If the automobile is running, it will probably undergo modest modifications when it reaches a warmer temperature.

[dramarena]

I lack any prior experience or knowledge about exhaust leaks and their occurrence.
This noise does not improve or decrease in volume as the engine becomes warmer. The issue was first seen just after driving, while the vehicle was parked and idling. However, it consistently occurred during warm-up following a cold start, as well as at every subsequent start.

[surveyunlawful]

Ticks often occur at the uppermost part of the engine, namely in the lifter and valve train components. There may be a little exhaust leak. Typically, knocks are caused by issues with lower end components such as main and rod bearings, or even a larger exhaust leak. Search for conspicuous soot marks in the vicinity of the exhaust. Occasionally, it is possible to detect the presence of a leak by physically feeling it with your hand. I would elevate the vehicle and inspect the underneath.

[dramarena]

Thank you for providing an explanation on the differentiation of matter. I eliminated the possibility of a rod bearing issue due to the fact that the banging sound was only present on one side (bank 1). I used a stethoscope, placing its tip on various sections of the engine such as the valve cover, exterior sides of the head, front chain cover, and all accessible components, including the exhaust manifold. When I placed the stethoscope on the exhaust manifold, I heard a very distinct and harsh banging sound that resembled metal hitting metal. I believed that this was the closest location to the piston wrist pin.
I would appreciate your opinion on this matter.

[RudolphNuclear]

It is possible that you are experiencing an exhaust manifold leak.

[dramarena]

Is there a method to verify whether the source of this consistent noise, occurring at warm idling and reaching up to 1200rpm, is really an exhaust manifold leak?

[surveyunlawful]

Inspect the junctions between the manifolds and the cylinder heads, as well as the connections between the flanges and the exhaust pipes. Search for dark or ashen smudges that might have been caused by the discharge of exhaust fumes. This task may be performed while the engine is in a state of low temperature. Initiate the engine and manually inspect the manifolds and connections by using your hand to detect any presence of exhaust gas leakage. On my item, the cats had been disassembled at the seams.