Approaching the inquiry on the comparison between valve stem seals and piston rings.

[vendimoto55]

Greetings, esteemed individuals.

I own a Mercedes-Benz S212 350 CGI vehicle with an odometer reading of 199,000 kilometres, and I have seen a significant oil consumption issue. Approximately 1 litre is used at a distance of less than 1000 kilometres. Previously, this was the situation prior to the replacement of the PCV valve. The sensation of burning remains quite pronounced.

I have been attempting to ascertain the condition of the rings or valve seals.

The symptoms encompass:

The phenomenon of excessive oil use.
Upon being left idle for an extended period, a visible emission of smoke is seen upon ignition in the morning.
When engaging in prolonged periods of idling or sluggish, stop/start driving, followed by abruptly accelerating in first gear at the base of a hill, a substantial amount of smoke is seen. On a particular occasion, I occupied the whole of the roadway. During the testing conducted yesterday morning, an occurrence of a misfire code was observed. The situation has been resolved and returned to its original state.

Based on my present analysis, I am inclined to argue that the seals are the primary factor. This phenomenon occurs due to the emission of smoke being observable only after the vehicle has been stationary for a considerable duration or has been idling for an extended period, resulting in the suction of oil by the crankcase pressure. It is posited that in the event of piston ring malfunction, a persistent emission of smoke would likely occur during instances of vigorous acceleration.

What are the prevailing opinions or perspectives held by individuals?

I am now attempting to ascertain the feasibility of replacing the stem seals while the engine remains in position, while still retaining the head. I am familiar with the rope approach and similar techniques. However, I am now attempting to ascertain if it is feasible to compress the springs in their current state.

Thank you in advance for your assistance.

[MBcarOWNER]

In the event that the valves are effectively sealing inside their respective seats, a compression test may be used to determine if the piston rings are responsible for any issues. If a decrease in reading levels is seen to improve after the introduction of a little amount of oil via the spark plug orifice, it is very probable that the issue lies with the piston rings.

[LostintheSea]

I too agree that the issue lies with the piston rings, however I am uncertain whether a compression test can effectively diagnose the problem. If the manufacturer of MB employs a 3-5 ring system, a common practise among many manufacturers, it is possible that just the oil seal rings have deteriorated while the compression ring remains intact. Compression may still be achieved. Additionally, there is a possibility that the bores may have been scored poorly, necessitating the necessity for a rebore.

[vendimoto55]

Thank you, gentlemen.

This topic is perplexing.

Gaining access to the boreholes for observation purposes is a complex endeavour. I am contemplating the possibility of only replacing the valve seals, since it is conceivable that I may proceed without the need to remove the engine. Examine the patterns and trends in consumption.

Undertaking tasks related to piston rings or bores entails much more complexity, in contrast to the relatively manageable nature of replacing valve seals, which I believe may be accomplished without professional assistance.

Does anybody have knowledge on whether the engine in question is equipped with cylinder liners or whether it just consists of straight bores integrated into the engine block? If one wants to increase the bore size, would it be necessary to get slightly bigger pistons or rings?

I express my gratitude.

[mortimerPAS]

Over time, valve stem oil seals tend to harden, leading to the undesired consequence of oil running down the stems when the engine is turned off. Consequently, this might result in the emission of blue smoke during the startup phase.

[MercedesMan98]

The observed correlation between the replacement of the PCV valve and the subsequent amelioration of oil usage implies a potential issue with the crankcase ventilation system. I would fully cleanse the whole of the system. Is there a potential obstruction, such as an oil separator or filter, that might be causing the issue? The occurrence of oil accumulation at low engine revolutions and low crankcase pressure, which is then expelled when the crankcase pressure increases during intense acceleration, has the potential to result in the abrupt emission of a visible cloud of smoke.

If the aforementioned explanation is insufficient, please continue reading for more information.

It is unexpected that a significant amount of oil would escape through hardened valve stem oil seals and stay unburnt, resulting in a substantial cloud of smoke under forceful acceleration. However, I am inclined to concur that if the smoke is not continuously present, the issue is more likely to be attributed to the oil seals.

If a cloud of smoke is sometimes seen during severe acceleration, without consistent occurrence, it may indicate that the bores and compression rings are in satisfactory condition. Have you conducted a wet and dry compression test? In the event that the wet compression surpasses the dry compression by a considerable margin, the optimal course of action would include replacing the piston rings, and in all likelihood, performing a rebore and installing new pistons. Regrettably, the only definitive method to ascertain the condition of the bores is by physically removing the heads to visually check them. Even a borescope examination may just provide information about the presence of scoring or damage, without offering insights into the extent of wear and its uniformity.

If it is feasible to do the task at a reasonably low cost and with no effort, I would proceed with the replacement of the valve stem oil seals in order to assess the outcome. If the oil consumption is deemed satisfactory, it is deemed satisfactory, but if that does not resolve the issue, and the compressions are satisfactory, I would be willing to consider replacing the oil control rings.

[Jul4ster]

The issue with my CLK was resolved by addressing the valve stem oil seals.

[aston_martin76]

During the deceleration process from speeds over 100 miles per hour, our previous W123 280TE vehicle emitted a noticeable blue-colored exhaust plume. The vehicle exhibits optimal cleanliness throughout the process of acceleration.

The problem arose from faulty valve seals, which allowed the vacuum to draw oil into the combustion chambers.

The area is thoroughly cleaned and free of any contaminants after the installation of new seals.

[vendimoto55]

Apologies for any potential lack of clarity in my previous communication. After conducting more mileage tests subsequent to the replacement of the Positive Crankcase Ventilation (PCV) valve, it can be affirmed that fuel consumption remains significantly elevated. At now, I have made alterations to all components shown in the accompanying image, namely pertaining to the PCV system, primarily in its external configuration.

I am inclined to concur with the proposed course of action. I am gradually becoming more at ease with the idea of doing the task of replacing the valve seals on the driveway and proceeding accordingly. In the event that no alteration occurs, I will want assistance from a qualified specialist.

May I kindly inquire about the process of tedium? I comprehend the underlying principle. However, when examining the bores, is there a noticeable increase in width that necessitates the use of larger pistons and rings? Is it often within acceptable limits that the regular components function? To ascertain the presence of cylinder liners in the M272 engine, one must use a method of investigation. In the event that the object has liners, it may be inferred that the process entails a mere act of substitution.

This is intriguing. I do not see any discernible outcomes or effects throughout the process of deceleration.

[MercedesMan98]

In the event that the bores exhibit significant wear necessitating reboring, as opposed to just honing, which involves a gentle abrasion with fine-grade sandpaper resulting in little material removal, the likelihood of requiring new pistons to restore optimal condition is rather high. If not, it is plausible that one may perhaps resolve the issue by only replacing the rings. The determination of the extent of wear may only be ascertained by removing the heads.

I am unfamiliar with the concept of the 'rope trick' (excluding the Indian Rope Trick, although its relevance is questionable). However, it is my understanding that professionals employ an adapter and air line (distinct from Virgin Airways, of course) to pressurise individual cylinders. This pressurisation serves the purpose of maintaining valve closure while lifters and springs are extracted, thereby facilitating access to the valve stem seals.
It is intriguing to note that I do not perceive any discernible sensations while undergoing deceleration.