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Q: noise when starts cold

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My GMC Sierra with only 4000 miles on it makes a rattling noise when it starts. Then the noise stops after hitting 210 temperature on it. This only happens in the mornings. It sounds like something is loose or just vibrating against other metal. I don't have any other problems with my truck. It's just the noise. It doesn't sound like a piston slap. Do you have any idea what is causing the noise?

A: Hello. This noise typically comes from the ...

Hello. This noise typically comes from the valve train. It is due to the design of the variable valve timing system. It is normal to make some noise, but it becomes worse if the wrong oil weight is used or if a good quality filter is not used. It can also be an issue within the system that needs to be checked such as a failing lifter. If you want to have it inspected, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose what’s causing the noise.

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