I have a 2023 Suburban with the LM2 with 37k miles. Over the last couple of months it has had a knock from the engine on cold start up. So, when I go to work and at late afternoon on return home. It lasts for about 2 to 5 minutes, then after closer to operating temp it is gone. Anyone else experience this? I've had it since new and have done all the scheduled maintenance. It does not happen every day, I guess about 75% of the time. My wife has a 25 Suburban with the LZO and it does not make that noise, though it only has 5k miles on it. Thanks in advance.
Knocking at cold start up
- Thread starter bdreker
- Start date
Sounds like piston slap to me. Not much you can do about it other than monitor it to see it doesnt get worse, let the engine warm up a little longer before getting on road. I would also let your dealer know about it so at least its documented in service history in case it turns into a warranty issue later on.
Did you switch oil filters? Whats oil pressure?
Last edited:
Maybe. My Vette has been doing it since I bought it in 2018. "Normal" for C5s, sadly. I havent had any issues with it, just let it warm up a bit longer.
Id just have the Subby looked at by the dealer, as its probably still under warranty. That way there's past documentation if theres a future problem. They will probably say "run it"
Id just have the Subby looked at by the dealer, as its probably still under warranty. That way there's past documentation if theres a future problem. They will probably say "run it"
Thank you all for your input. Definitely going to the dealer, we live in a remote area so it's a day trip to do so.
I do let it warm up before hitting the road.
Oil & Filter always changed at 5K. Pressure is about 20 at idle, which is normal, and hard to read on a gauge that goes to 120
Weird that it doesn't do it 100% of the time. No knocking noise this morning.
I do let it warm up before hitting the road.
Oil & Filter always changed at 5K. Pressure is about 20 at idle, which is normal, and hard to read on a gauge that goes to 120
Weird that it doesn't do it 100% of the time. No knocking noise this morning.
Try a fuel additive and see if that helps, I’ve heard some people complain about the injectors being noisy in the lm2.
Thanks NC, I've been using XDP and just bought AC Delco Fuel system cleaner and will add that my next fill up.
Also, they make different noises when they are in regen. Might want to see if it’s regenerating when it’s making the noise. I just switched to the new gold power service with injector cleaner and dpf flush, it actually works as advertised.
No truck will regen when coolant temp is below a threshold of 165-175* engine coolant temp. Since this is only when cold, its a non issue
I agree here 1000%.
Get that report in at the dealer and it may save your ass in the future. My 2013 GMC terrain had been brought into GM a few times for oil consumption with the 2.4L. Sure shit, got that covered due to previously history of oil consumption where they rebuilt the engine at ~149k miles thanks to some help from my local dealer who owed me a favor or two.
Update for those interested:
I took my vehicle to the dealer. They had it for 3 days and could not replicate the knocking noise at cold start up. I gave them a sound recording of the knocking, but they said they can't tell where its coming from just from the recording. Before I drove it to the dealer, which is a 3 plus hour drive, I added a quart of AC Delco Premium Diesel Fuel System Cleaner, Part #19435374. So, I Figured that the knock was related to an injector. I had no knocking for 2 days after picking up the truck from the dealer. Then, yesterday morning it had the knock again, but this morning it was fine, no knocking. Crazy! At least it is documented for warranty purposes.
I took my vehicle to the dealer. They had it for 3 days and could not replicate the knocking noise at cold start up. I gave them a sound recording of the knocking, but they said they can't tell where its coming from just from the recording. Before I drove it to the dealer, which is a 3 plus hour drive, I added a quart of AC Delco Premium Diesel Fuel System Cleaner, Part #19435374. So, I Figured that the knock was related to an injector. I had no knocking for 2 days after picking up the truck from the dealer. Then, yesterday morning it had the knock again, but this morning it was fine, no knocking. Crazy! At least it is documented for warranty purposes.