I had the same sound after flushing my coolant. I made the mistake of not opening the coolant control valve when I did the flush. I burped it every few days for a couple weeks, and the problem went away. With a cool engine, just pop the radiator cap and squeeze the upper radiator hose. If you got rid of some air, the fluid at the radiator cap will be lower, so top it off. You can also try the same technique with the air relief valve open. The relief valve is on a hose located between the battery compartment, the firewall, and the plenum. It is kind of hidden under another hose or conduit and just takes a Phillips screwdriver to remove. Good luck.

 

TB is Throttle Body. There's two small coolant hoses connected to the upper collector (plenum) right behind where the TB attaches to it. You would have needed to disconnect these if you completely removed the upper plenum or if you installed the MD Iso-Thermal TB gasket instead of the shut-off valve. Their purpose is to heat the TB and prevent icing on the plate. See the diagram... items 9 and 11 represent the hoses and their connection...

11 is the hose that the MD manual shut-off valve would have been intalled in.
Tony's manual doesn't actually call for disconnecting them unless you installed the Iso-Copper gasket which has it's own coolant connections that replace those on the plenum.

Either way, if there's no leak and your coolant isn't low you probably just need to burp the system.
Does this help?

 

i did disconnect those hoses because i took the upper plenum all the way off. Im pretty sure i reconnected them correctly though. Ill have to recheck my coolant levels. I figure the car would overheat if they were low, and the car hasnt overheated yet.

 

With the exception of a few correct answers to your question I've never seen sooo many noob answers! You have an air bubble in your radiator cooling system, run your G with the heater on and the radiator cap off, that should remove the noise you're experiencing. You can also find answers to your questions at www.infinitihelp.com or SEARCH here on DRIVER for an occasional correct answer....
Gary

 

ill give that a shot! thanks!

just for my info, should i start this process with the car cold? like after i get off work, go to my car, take off the radi cap and turn on the car with the heat blasting? how long should i let it run?