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Knocking noise in the engine

Hi, my friends Hyundai Santa-FE 2007 makes a knocking noise like a hammer hitting the engine when she starts the car and drives. What could that be?

Here is a photo of the Hyundai Santa fe 20007 with the “knocking noise” that sounds like a hammer hitting the engine. Any ideas?

Please be more specific of when the knock occurs. Does it knock when idling in Park? Or does the knock begin when shifted into gear? Or possibly the car must be in gear and moving? It might be worthwhile to check the oil before starting the engine again.

One more question:
has anyone checked to see if there’s oil in the engine?
Are there any warning lights illuminating?
How many miles does the car have on it?

Okay, that’s three questions. But they’re critically important, so please forward the answers.

Could be a loose connecting rod = $$$$ but that is rare now. Could be a heavy case of piston slap. Light slap is ok but heavy slap can get worse. Could be a collapsed hydraulic valve lifter if it does not have solid lifters. Could be a loose pulley in the serpentine belt train. A loose cam chain can make a knocking noise but that should go away when the oil pressure almost immediately comes up to actuate the cam chain tensioner. Could be something else but there are a few guesses for you. A mechanic’s stethoscope might reveal the source of the noise. Sometimes simply opening the hood with the engine running can reveal the source of the noise.