When I start my car it is loud but after a couple on minutes it quiet’s down could you tell me why
When you first start your car it will be in high idle mode to get the engine up to operating temperature faster. Once it’s up to operating temp, the idle goes down to normal. This obviously takes longer in cold weather than warm weather
You could have a crack in the exhaust manifold. As the engine warms up the metal expands and the crack closes.
Yosemite
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Where is the noise coming from? If you want to get a better idea, open the hood then start the SUV. Now get out and listen under the hood for the noise. Maybe you can pinpoint it.
“As the engine warms up the metal expands and the crack closes.”
I don’t think so. Back in high school physics we learned that the hole expands as the metal expands. (Of course, there were only two laws of thermodynamics back then 
)
If you had a gap between two metals that had different thermal coefficients of expansion, maybe there is a situation where the gap would close up.
That’s for an unconstrained plate. An exhaust manifold is constrained by the much cooler engine, so cracks in certain places can close up upon heating.
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