My range hood is making a knocking sound as soon as I turn it on.

Check your AC compressor & clutch open the hood,running with AC on

You need to take it to a garage as soon as possible. Knocking from the engine bay usually means sever problems. catch it before it gets worse

Pull a plug and check to make sure that you put the correct plugs in. If they were the incorrect heat range you can burn off the electrode and it could have got stuck in the valve, causing the knocking sound. Use a long 3/4 extension as a stethoscope to try and locate which side of the engine the sound is comming from. Then do a compression check to find the cylinder with the stuck valve.
Pull a plug and check to make sure that you put the correct plugs in. If they were the incorrect heat range you can burn off the electrode and it could have got stuck in the valve, causing the knocking sound. Use a long 3/4 extension as a stethoscope to try and locate which side of the engine the sound is coming from. Then do a compression check to find the cylinder with the stuck valve.

The smoke under hood means that u need replace gasket between exhaust pipe and engine but smoke and knocking is not very good, it looks like your engine pistons has cracks and u r loosing oil by smoke time to time, i'd buy used engine from crashed car with less miles on it

It tercould be a blend door motor,Try get in turn off everying.Then start it and if you here anything,if not turn on the heater and turn the hot and cold switch. see if it stops.a nother thing open the hood start it up check the passenger front end see if you hear it up there. if so i think the air compressor for air ride is there.

First check the grade of 'Gasoline' now days they add ethanol,Which can cause engine knock, Second lift the " hood' while auto mobile has been off and cool to prevent cooling fan injury,look for any obstructions,such as a wire's harness,Third i would check catolitic converter for loose heat shield.

make sure the fan blade not touching anything. make sure are clean the grease sticking to the blades can make the fan go out of balance

you can reseal the hole with aluminium tape
you can use screws with metal flat washer that has a rubber backing

SOUNDS LIKE A ROD KNOCK..ON THE BOTTOM END ... CHANGE THE OIL AND CHECK ITS CONDITION... SOUNDS LIKE U MAY HAVE A CAR WITH SOME MILES ON IT... TRY AN ADDITIVE OR USEING A THICKER OIL ..

There is definetly somthing blocking the air from escaping, either the duct is blocked or the installer did not remove the metal plate which opens the fan up for it to be able to evacuate.