Q: If the air is too cold, motor knocks on startup

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The motor in my 2010 GMC Terrain rattles and kinda knocks when I start it up cold in the morning. The sound goes away but it is just enough to make me concerned that something may be wrong in the engine. Is it possible for the cold motor knock to not be a problem? Can this naturally happen? My car is at 38,000 miles after all, and I always make my scheduled oil changes.

As strange as it may sound, the oil filter that was used during one of your oil changes may be the root cause. GMC Technical Service Bulletin (TSB) 10-06-01-003C has detailed technical information showing that some non ACDelco oil filters do not meet the demands of the oiling system and can restrict oil flow to the valve lifters or cause aeration in the oiling system to the lifters, thus causing a rattle noise on startup. The most likely reason that the noise goes away is that the lifters become pumped back up and it all goes back to normal. My recommendation is to have the oil changed by a certified mechanic from YourMechanic, and make sure the correct ACDelco (or equivalent) oil filter is used and keep up on those oil changes. If the noise persists, then some diagnosis is needed. A certified mechanic can help diagnose the noise with an early appointment, as this noise most commonly happens first thing in the morning.

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