Engine - Knocking on Cold Start Explanation
INFORMATIONBulletin No.: 01-06-01-028B
Date: October 03, 2011
Subject: Engine Knock on Cold Start
Models:
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models
2002 Cadillac Escalade (2WD)
Equipped with 4.8L, 5.3L or 6.0L Engine (RPOs LR4, LM7, L59, LQ4)
2007-2012 Cadillac Escalade Models
2007-2012 Chevrolet Silverado
2007-2012 GMC Sierra, Yukon Denali, Yukon XL Denali
Equipped with 6.2L Engine (RPOs L92, L94, L9H)
Supercede:
This bulletin is being revised to update the Models section. Please discard Corporate Bulletin Number 01-06-01-028A (Section 06 - Engine/Propulsion System).
Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.
This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.
Important
At this time, attempts to repair this condition by replacing the engine assembly or pistons are not recommended.
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 your District Manager Aftersales (U.S.) (in Canada, District Manager - Customer Care and Service Process (DM-CCSP).
Disclaimer