2008 6.6 LMM Engine Snapping Sound

[EdSpaek]

Have read threads about a loud snapping sound similar to a lifter but much louder that can occur especially after an oil change. My 2008 LMM just developed this sound after my second oil change at approx 13,000 miles

Appears to come and go but it very loud when it occurs

Any thoughts-the dealer just changed the oil and filter along with the fuel filter

Other than this the truck runs great

[Duramaster]

You probably have this concern. I would worry about it no further. This noise has been around in the DMAX since day one. And even though the bulletin "REMOVES" the LMM from the bulletin, I still hear the tapping occasionally in the LMM's.



Subject: Information on Engine Ticking Noise


Models: 2001-2007 Chevrolet Silverado (Classic)

2003-2009 Chevrolet Kodiak C4500/C5500 Series

2006-2009 Chevrolet Express

2001-2007 GMC Sierra (Classic)

2003-2009 GMC TopKick C4500/C5500 Series

2006-2009 GMC Savana

with 6.6L Duramax™ Diesel Engine (VINs D, 1, 2-- RPOs LBZ, LB7, LLY)




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This bulletin is being revised to add model years and remove RPO LMM. Please discard Corporate Bulletin Number 02-06-01-022G (Section 06 -- Engine/Propulsion System).


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Some of the above vehicles may exhibit a random ticking noise that is most audible on an engine with a coolant temperature of 70°C (158°F) or higher and from idle to approximately 1500 RPM. 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 inside the vehicle at idle such as when sitting at a drive through window. 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.

This noise is caused by the relationship of the engine cylinder block, crankshaft journals, bearing inserts and the oil film. This relationship may allow a vibration that resonates through the cylinder block and is heard as a metallic ticking noise. The noise could be described as an irregular ticking or clacking sound, like random typing on a mechanical typewriter.

This condition has been present in diesel engines produced for the last 20 or more years. The overall noise reduction in engines produced today makes this noise seem new when, in fact, it was masked by other noises in the past. Many manufacturers such as Isuzu, Hino, Mitsubishi, and Nissan report a similar condition in their diesel engines. Testing and engine teardowns with this condition reveal no condition that would affect reliability or durability of this engine.

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 at the numbers listed below for further information.

Division
Number
Deaf, Hearing Impaired or Speech Impaired*

Chevrolet
1-800-222-1020

8:00 AM - 11:00 PM (EST)
1-800-833-2438

8:00 AM - 11:00 PM (EST)

GMC
1-800-462-8782

8:00 AM - 11:00 PM (EST)
1-800-462-8583

8:00 AM - 11:00 PM (EST)

Canada
1-800-263-3777

(English)

1-800-263-7854

(French)

7:30 AM - 11:30 PM (EST) (Mon-Fri)

7:30 AM - 6:00 PM (EST) (Sat)

[EdSpaek]

Appreciate the response. I will worry no more