Diesel Piston Cleaning in Engine 4

[chuckfrench]

In diesel engines carbon build up, leading to stuck piston rings, can be a problem. Is there a product that can be safely used to clean pistons and free stuck rings in a turbocharged, diesel engine, without removing the pistons from the engine? Commercial products appear to be limited to non-turbocharged, gasoline engines.

 

[ivymike]

some people have successfully used steam (introduced via the intake ducting into a running engine).

 

[chuckfrench]

I am concerned about where the loosened carbon might be lodged, potentially blocking oil passages in the turbocharger. Has experience shown this concern to not be valid? If the oil filter is in the by-pass mode, it is possible that oil supply from the pan is unfiltered.

 

[ivymike]

I would generally expect that the carbon removed by this method would be limited to soft deposits on the top land - with hard deposits and anything shielded by the top ring left intact. The soft deposits removed from the top land would likely exit via the exhaust with little/no trouble, unless you have a dpf in the way.

 

[BrianPetersen]

In the VW diesel world, stuck piston rings almost always have one of two causes:

1. Some clown is not using the correct grade of synthetic oil that meets VW's oil standard, or;

2. Some idiot is using vegetable oil as fuel - especially if they are not heating it up enough.

Best thing is to not have it happen in the first place. If it happens and is bad enough to cause trouble, there is only one proper fix ... the engine has to come apart.

Sold my previous VW diesel at 462,000 km, never had this happen.

 

[romke]

fouled up pistons and stuck rings should not occur when using the correct grade of oil for the correct oil change interval with good injectors, a working cooling system and the engine correctly loaded. when idling a lot and commuting in stop&go traffic it may be necessary to change the oil more often.

whatever the cause, a good quality engine oil with sufficient detergent/dispersant properties should not only be able to prevent this from happening but might also be capable of cleaning up the engine internally - although that may take up quite some time, say up to 20000 km or several oil changes.

there are some substances available that might do the trick, however, that is a costly way of buying a little detergent/dispersant dispersed in a usually not so good carrier oil.

in my view using the correct grade of oil and sufficient load of the engine should be able to cure the problem, if not dismantling and cleaning is the only alternative.

 

[ivymike]

I've seen several examples where diesel engines would accumulate significant carbon deposits, eventually leading to bore polishing, ring sticking, and elevated oil consumption, even when run with the correct grade of oil and with all-new (initially) parts. It was a matter of injection timing vs. emissions constraints vs. the real-life operating cycle used by particular customers (a few percent of the engine population, and I'm not talking about city driving or idling, but regularly running at a few particular bad spots on a load-speed map). It was made significantly worse by a particular popular brand of oil (at the same grade), but was not fully mitigated regardless of oil type selected. With enough work the problems were eventually duplicated in a test cell and the manufacturers were able to make system changes to prevent future occurences. I believe that the oil manufacturer may now have an internal qualification test procedure named after one of the engine models in question.

 

[tbuelna]

chuckfrench,

Some larger bore diesels actually use something called an anti-polishing ring around the upper end of the cylinder liner to limit the build-up of carbon deposits at the piston top land region.

Sounds like it's a little late for your situation though.

 

[chuckfrench]

Thanks to all for their interest and contributions. I believe Ivymike has come closest to the cause of the problem in this case. Smyptoms seem to be unique to applications running intercity delivery service on mountainous routes requiring frequent variations in engine speed and load. Oil quality and service interval are good as determined by oil analysis. Because the application has limited volume, it is highly desirable to develop a service solution rather than an engine calibration change. Your collective comments confirm that a service solution is unlikely.