duramax knocking noise

[msgbob]

I have a 2002 2500HD with Duramax and Allison, 2wd crew long bed, about 75K miles. Just recently it started a fairly loud kncking when cold that goes away after a few minutes. Sounds like its coming from the right side of the truck, but I have not been able to pin point it. I'm a former ASE certifed mechanic, and do all my own work as a rule, I'm not new to vehicles, but aren't finding much out on this. Any thoughts?

[pm26]

I have an '83 Mercedes 300Sd with a turbo diesel engine and it too knocks when cold. This is a well known knock called "injector nailing". After the engine warms up, the knocking goes away. This car uses mechanical diesel injectors with an internal spring. As the injectors get older (about 100k miles or more), the spring gets weaker and and the knock you hear are the injectors pounding. Replacing the injectors with rebuilt ones generally cures this. Also, using a diesel injector cleaner by bypassing the fuel tank helps lessen the noise.

 

You may want to have the injectors cleaned to see if the noise goes away.