Stolen from another thread.
#16-NA-372: Information on Diesel Engine Ticking Noise - (Nov 14, 2016)
Subject: Information on Diesel Engine Ticking Noise
Involved Region or Country
North America, and Israel (Export Dealers please contact your Local Technical Assistance Center if there are additional questions.)
Additional Options (RPO)
Equipped with Duramax™ Diesel Engine (RPOs L5P)
Condition
Some of the above vehicles may exhibit a random ticking noise that is most audible on warm engine in idle and elevated idle condition with fresh oil. The noise usually is most noticeable at the rear of the driver's side front wheel well. Customers may also comment about hearing a tick noise in drive through. All 6600 Duramax™ diesel engines have this condition; however, some are more audible than others. Engine build variation from engine to engine contributes to differences in perceived volume. All Duramax™ engines are manufactured to very close tolerances to meet the durability and reliability standards.
Cause
This ticking noise is caused by oil bubbling and excited by the V8 configuration and combustion sequence. The noise could be described as an irregular ticking or clacking sound, like random typing on a mechanical typewriter.
Information
This condition has been present in diesel engines produced for the last 20 or more years (refer to the latest version of Bulletin No.: 02-06-01-022), and does not have any impact on engine reliability and durability. The overall combustion background noise reduction in the new engines made more audible the known ticking. Many manufacturers such as Ford, Isuzu, Hino, Mitsubishi and Nissan report a similar condition in their diesel engines.
Dealers should not attempt to compare any customer vehicles exhibiting this noise with other similar vehicles as the noise is different from vehicle to vehicle and this may lead to the incorrect conclusion that the vehicle has a condition. This noise is a normal operating characteristic of the engine. This noise has no short or long term effects on the engine. Do not attempt repairs for this noise.
Important: Replacing the engine or internal components for this noise will not reduce or eliminate the noise.
Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise them to contact Customer Assistance.
