The CDL training school I work for bought a Freightliner FLD tractor with a Cunnins M11 turbo diesel engine. The tractor has sat for several years unused. The Jake engine brake is not working. We were advised by the repair shop-they feel the cause is engine sludge build up in the Jake brake valves in the top of the engine, due to the engine not being ran for such a long time. They recommended using an engine crankcase cleaner/desludge product but could not recommend a brand. Every one we have looked into states they are not for use in turbo charged engines. Can MMO be used safely in turbo charged engines without damaging the turbo or plugging the turbo oil supply lines with loosened sludge?

Most of the products that you have looked at for removing the sludge are mostly likely 100 % solvents.  Marvel Mystery Oil, while containing some solvent, is mainly oil and will slowly dissolve the sludge and keep it in suspension until you drain the oil out of the engine.  Marvel is safe for turbo engines and will not clog or plug the oil supply lines.

thank you Rich. We will give it a try.