Rescued an E350 CDI coupe from certain destruction!

[Mistral]

Greetings,

I acquired a 2011 E350 CDI coupe in February of this year. It is equipped with the 265bhp OM642 engine.
The vehicle had defects at the time of purchase, which I shall detail. Since I do my own work, this was not a concern, since I intended to perform a comprehensive suspension overhaul and undertake any necessary preemptive maintenance and repairs, consistent with my approach to previous Mercedes vehicles I have had.

The EML light illuminated, and the vehicle entered limp mode after five minutes of operation.
The engine temperature gauge was not reaching the appropriate temperature.
Audible knocking sound emanating from the front end
Vibration in the vehicle while navigating gentle curves at highway speed
Vibration when braking
Ambiguous, imprecise, and unstable sensation while navigating gentle curves at highway velocity.
General unease when operating a vehicle
Petroleum discharge
Substantial oil usage
Upon bringing it home and connecting it, the DPF seemed to be the source of the problem, namely, it was obstructed. I changed the thermostat, believing it would be inhibiting the car's regeneration process due to inadequate temperature; however, this did not cure the DPF problem, although the temperature gauge now functions properly.
I then examined the DPF sensor data, which seemed to be functioning properly. I replaced the sensor with an authentic one, since the previous component was aftermarket; however, this was not the issue, as the pressure and soot levels remained elevated, preventing regeneration.
During the sensor replacement, I applied a cleaner to the DPF and idled the engine for 15 minutes. A subsequent inspection revealed a significant reduction in pressure. However, two minutes into a test drive, I observed an increase in RPM at idle, accompanied by substantial smoke and the odour of burning rubber. Result! The automobile was autonomously regenerating, and concurrently, the engine management light extinguished.
The automobile now operated efficiently in terms of the engine, so I began gathering all the components for the further work I had planned.
Upon commencing the oil cooler seal repair, it became evident that the turbocharger was compromised upon removal, which, if overlooked, could have resulted in catastrophic engine failure. The vehicle operated normally without discernible smoke; however, it did emit smoke during regeneration intermittently, which I attributed to oil leaking from the oil cooler. In reality, the smoke originated from oil leaking from the rear of the turbocharger onto the diesel particulate filter, and the intake wa
I have had many OM642 vehicles, and my current one, with 230,000 miles, continues to perform reliably at 800 miles per week, which has left me perplexed by the reports of frequent failures in the later model engines. Could the DPF be responsible for their demise, given what occurred with mine?
The failure of my turbo was attributable to a clogged DPF, which permitted an accumulation of excessive heat and pressure at the rear of the turbo, resulting in seal rupture. All pipes connected to the rear of the turbo exhibited indications of elevated heat via discolouration.

All tasks have been completed, and the vehicle operates well; all intakes have been cleaned.

[Mistral]

All components, including the intake manifolds, throttle body, EGR flap, and EGR valve, were thoroughly cleaned, with all seals changed and a comprehensive service conducted simultaneously.
I replaced all front-end suspension arms, shocks, and springs, both front and rear.
I am meticulous about the performance of my Mercedes. Although it operates flawlessly, I have yet to repair the rear subframe bushes and arms, indicating more maintenance is required. I am now relishing the ability to operate the automobile proficiently, and it is an incredible powerhouse!

I intended to do a gearbox service as well; but, after receiving an estimate from PCS, it is not justifiable due to their very reasonable pricing. Therefore, I will be scheduling an appointment soon.

I developed a spreadsheet to monitor my expenses and completed tasks, as well as those remaining; all indicators are green, indicating satisfactory progress.

[Mistral]

The genuine expense of owning a Mercedes is substantial, although it is well justified.

[Mistral]

And that is without effort, since I completed all the job!

[developer]

Excellent work! I hope the automobile was inexpensive to acquire.

Was there a genuine problem with the oil cooler seals, or was it a precautionary measure since the turbo was removed?

[Mistral]

Thank you, the vehicle was inexpensive to acquire at the time due to its Euro 5 engine. I have spent more on achieving accuracy than the cost of the car.
The oil cooler seals were deteriorated, resulting in significant leakage.

[Mistral]

Upon removal, it had the orange seals, which have subsequently been replaced with the purple ones.
The most intriguing discovery was that the EGR flap, which links to the throttle body, was completely obstructed. The aperture intended to measure around 2 inches by 1 inch was entirely obscured by a 10mm thick layer of carbon accumulation. I was astonished that an EGR problem flag did not appear.
Everything has been meticulously cleaned, and all seals have been replaced.