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Q: Engine knock

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My dad xplorer is as runner no fine one day we had a great freeze next am been knocking every since My explorer was tuning fine we had a temp drop overnight 2days ago now it knocks so bad I'm afraid to do I've it? What caused this?
My car has an automatic transmission.

Hello. If the engine knock started after a few cold nights then it may be possible that it is related to the engine oil. Engine oil becomes thicker at lower temperatures, which makes it more difficult to pump for the engine the colder it gets. This may result in knocking or lifter noise if the engine struggles to pump the more viscous oil. The noise will usually go away after the engine warms up. I would check the oil to make sure that it is not low, and change it if it is dirty. If you are approaching the colder part of the season then it may also be a good idea to use a lighter weight oil, as lighter oils will flow easier and quicker at lower temperatures. It may also be possible that the knocking may be related to an engine performance issue, though usually the check engine light will come on if this is the case. If you are unsure, I would recommend having a professional technician, such as one from YourMechanic, come to your location to diagnose what may be causing your noises.

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