doing what J suggested is the way to pinpoint where the noise is coming from. Doesn't have to be a wooden handled screw driver, (I don't have one long enough) can be any rod. Acts like a stethoscope, where ever you put the other end not in your ear it will pick up and send the noise right to the bones in your ear...you will find it.
Obviously the motor is running and you are sticking a rod or long screw driver into places with moving parts...use your head.
Look on the bright side for now, could be a loose mounting bracket, motor mount, or one of the steel hoses. Might be an accessory, the rod will tell you for sure where the noise is coming from.
Any metal should be real fine, like a paste...drain the oil and use a magnet to find any in it. If you have something clanking it's bound to be chewing...you should find shavings of metal. Many drain plugs are magnetic, yours maybe.
The rod in your ear (not actually in your ear by the by, kind of push on the tip of your jaw bone) can be used to find any noise in something...wanna find that mouse chewing in your wall before taking aim? :)
Think about the principle behind the rod and apply it to anything incorporating a "rod". Many "rods" in construction, break the transmission of the noise going down the rods and your house will be much quieter. Insulation is commonly used because it slows the vibration of the rods. I've heard of houses deemed unlivable due the the framing members singing loudly. Even a strap will transmit sound from one end to another. You no doubt have connected two tin cans together with a string and talked to someone on the other end.
I use a 1/2" solid metal rod...somethings transmit sound better than others, but they all will work, even a wooden one. PVC will probably work.