Weird Pew Noise After Duramax Starts.

I'm posting this here because I find the TW community much more helpful than the Duramax community. Maybe some with more experience will know what this sound is. Thanks for the help!

So a couple of weeks ago, my truck started making this short "pew" noise directly after it starts when the engine is cold. Only last like a second and it happens just as soon as I release the key from starting. Seems to be worse if its colder outside but will even do it when its above 60F. Once the truck has been driven and reached operating temp, it will not make the noise when you start it again. the truck pretty much needs to sit for a day and completely cool to make the noise. The truck starts just fine, runs and idles just fine. I have an Insight CTS and all temps and pressures are the same as they always have been. The truck is up to date with all maintenance. I have realized though that the noise started directly after an oil change! I changed my oil on the 5th and I first heard the noise on the 9th and its very possible that I didn't drive any between those days. Changed oil with 10qts of Rotella 5w40 and a Mobil 1 filter, same as always. The only thing I did different was I changed out my factory oil drain plug with a PPE magnetic plug. Feel like this shouldn't be related but its the only thing "different" I did during the oil change. Please see link for video of noise.

https://youtu.be/q0b9AQzZrF0

Truck: 2011 LML Silverado 2500HD CCSB Z71, Leveled, Bilstien 5100, ICON Uppers, Fuel PUMP 18" Rims, Nitto Terra G2 295/70R18, 4" DP Back No Muff, SDP Cold Side Charge Pipe, S&B CAI w/ Volant Powercore Filter, EGR Blocker Plates, H&S Tunning, AFE DFS780 Lift Pump, DEF Tank Removed, Insight CTS, Airlift Bags, B&W Companion.

 

Service Information 2011 Chevrolet Silverado - 4WD| Sierra, Silverado VIN C/K Service Manual| View All Bulletins | Document ID: 2613157 #PIP4898: Duramax Diesel EngineOil Pan Whine Noise - (Mar 30, 2011)
Subject: Duramax Diesel EngineOil Pan Whine Noise
Models: 2010-2011 Chevrolet Express, Silverado 2010-2011 GMC Savana, Sierra Equipped with the 6.6L Diesel Engine RPO codes LGH or LML.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern: Some vehicles may exhibit an engine buzz, moan, rattle, whine, or vibration type noise that can typically be heard at idle or low RPM. The noise may be hard to duplicate, change in intensity, and/or phase in and out when listened to for a long period of time.

The noise will be the loudest near the bottom of the oil pan. The noise is generated by fluid pulsations inside the oil pump. Oil pressurereadings will be normal.

Recommendation/Instructions: Engineering is aware of the concern. If a dealer has noticed that the whine noise is coming from the oil pan area please do not attempt repairs.

It is possible that all 2010-2011 6.6L engines (RPO codes LGH & LML) will have this noise in varying levels. Testing and engine teardowns have been performed and reveal no condition that would affect the reliability or durability of the engine.
The repair for the whine noise will be a revised oil pump. This PI will be updated when new information about the oil pump becomes available.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

I really appreciate the reply and info. I am pretty certain that I have heard the whine noise, typically after an oil change. This noise, however, is new. I think? I feel like I would have noticed in the past. My plan is to have my wife start the truck next time and I can be under the hood to see if its coming from there. Or I may try laying under the truck and see if it is coming from the pan. As of now, my plan is to just keep using the truck as its performing just as good as it always has. Just don't think Ive ever heard this noise at startup though.

 

My guess it's either a sticking starter solenoid (pinion gear not retracting from flywheel as quickly when cold), or simply some air valve making a whistling sound when cold. Take it to a diesel mechanic with experience on Duramaxes if you want a real answer.

 

My 2016 LML started making the same sound. Did you ever find out what it was?