2017 Yukon Loud Rattling/Knocking Sound at Startup

Tabitha Zapata · November 16, 2021

2017 Yukon making this loud sound around 75k miles, at the morning start up, or if it has not been driven for several hours.

Local mechanic hasn’t figured it out. Have not tried dealership yet. Want to know what I’m getting into before I take it there.

It sounds like it’s coming from under the car.

CamGTP · November 18, 2021

That's a tough one to say.

The first whine/whirl sound just after starting is the oil pump, that is a very common thing to hear and is heard far more on cold engines and in cold climates. After that the ticking sound to me sounds valve train related, like a lifter is still being pumped up with oil before it quiets down. If you're hearing it under the truck and towards the back I'd think it's one of the rear cylinders. If the engine doesn't make the sound when it's warm then that is kinda what I would suspect.

I'd be curious how long it's been since your last oil change or how long you run it between oil changes.

Tabitha Zapata · January 16, 2022

I get oil changes every 3-4k miles. It won’t make the noise for the first week after an oil change but then it will start back up get. Gets more knock the closer to a new oil change.

Supreme Pizza · January 16, 2022

2 hours ago, Tabitha Zapata said:

I get oil changes every 3-4k miles. It won’t make the noise for the first week after an oil change but then it will start back up get. Gets more knock the closer to a new oil change.

I would an engine flush and then change the oil weight to the heaviest allowed in the owners manual. Probably 10w40 (depending on ambient temps).

The engine flush costs $10 at the parts store, and can be added to the oil just before the oil change.