reorganize your workspace ....
end 2006 - Saved a G5
someone said to me his quad wasn't cooling at all
only making a terrible noise
he had to shut down the quad
i saw the G5 on the floor, onder the table
at the floor level, there are usually 'hovering' dust particles
opened the quad
disassembled as much as possible,
cleaned every part thoroughly
problem solved ......................