Loud Diesel Sound

Could be engine knock.

Get it checked out ASAP.

Make sure you have oil as this engine is known for burning and if you have no oil you will get sound.

Could you have an exhaust leak?

After starting car, walk around car,look under hood, under middle of car and under back ... where is it loudest?

it would help to attach a recording of the sound.

Thanks for all your suggestions. Thank goodness it doesn’t appear to be the engine itself, as I’ve since had the oil check and had it put on a diagnostic computer and no codes are coming up. I’ve also had an oil change, the motor mount replaced, coils, & spark plugs. Yet it’s still making the sound. So it’s now running like a sewing machine, just a loud heavy one lol

You have exhaust leak from a donut exhaust manifold seal, where it connects to exhaust pipe.