My 2000 maxima makes a loud noise under the hood when it is idling sometimes. It happens on warmer days and when the car has been running for a while. It is t overheating and I looked under the hood while it was doing this and the radiator was vibrating. Any idea what could be causing this?

 

You need to just start safely touching things to see what might be loose. This could be impossible for anyone to help u with without a video. No way of knowing what's going on.

 

If it's overheating, I would address that issue before any rattling noise. Heck, it could be the water pump going bad.

 

You also might wanna make sure your radiator upper and lower support bushings are there and not worn/dry rotted! But the noise could be damn near anything! Tensioner, belt, a/c compressor, alternator P/s pump, crank pulley, w/p, timing chain, etc....You do have arms and hands? If so you might want to put them to use Jsbeeson...If you're still lost you can remove the accessory drive belts 1 at a time to narrow it down to what the source is...while the belts are remove be sure to check each items rotating pulley for roughness, or any bearing wear by rocking the pulley in the 3 to 9 o'clock and 12 to 6 o'clock axis! Once all the belts are removed and you run it for a few minutes and it's still make noise then you'll know it's the w/p or timing chain! Good luck! Process of elimination....

 

You may have a radiator fan motor that is about to completely fail. With the engine turned off, try wiggling the fan blades. If you can detect any wiggle, that motor has bad bearings.

 

Yes, sounds like the radiator fan. It is not overheating. The radiator fan cycles on and off to keep the engine running at the correct temperature.