Engine sounds like a diesel during cold morning starts

[phillypoet313]

I have a 2002 4.2 I6 LS Trailblazer that makes somewhat of a diesel sound (engine) in the morning, then quiets after a few miles. Can anyone suggest any type of oil or additive for this? I have no issues with the truck, just the annoying sound from the engine (during cold morning starts...only).

 

[Wooluf1952]

Are you talking about noisy lifter clattering sound? Or a fan roar?

 

[The_Roadie]

Or a cracked exhaust manifold that seals up (for now) when it gets warm.

 

[phillypoet313]

Are you talking about noisy lifter clattering sound? Or a fan roar?

"Exactly"

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"Exactly"

lifter clatter, then quiets during warm up.