Cm2450 knock

[Khera]

Hey guys. I got a 2022 peterbilt 389. 350k miles. I bought the truck new. For the past 3 months I’ve been noticing a knock on cold starts. They kinda. Goes away when oil temp reaches no operating temperature. The knock seems to be coming from air compressor area front left of motor. FYI I do have upgraded high output air compressor. I got overhead ran last week as well. Didn’t make any difference. I ran injector performance test as well and all of em passed. Also did the fuel system leak down test and didn’t find anything? What are your guys thoughts on this?

[windowrattler]

Shutting down injectors one at a time could help isolate it to a cylinder.

[Khera]

(05-12-2024 )windowrattler Wrote:  Shutting down injectors one at a time could help isolate it to a cylinder.

I did but by the time I had started the test the engine was warm and the knock had gone away. So the test didn’t help. Am going to try again and make sure the engine is cold.

[Khera]

And the knock is not Consitant. It goes knock knock knock knock knock then nothing for half a sec then knock knock again.

[Rawze]

(05-12-2024 )Khera Wrote:  And the knock is not Consitant. It goes knock knock knock knock knock then nothing for half a sec then knock knock again.

Does it do it more when the air system is empty, or when its up all the way?.

Maybe try it with compressor output line disconnected, to unload it?.