61 dlp loud internal loud noise...help!

[Therealcmac]

Hi, thanks for reading, sound is similar to water running through pipes is best way to describe it. Goes away after tv has been off all night and comes back about half way through the day, definately something that is spinning, keeps going for about 30 sec after I have turned set off, depending on how long it has been on. It doesn't seem to be the fan that is readily visible, is there another fan? As I am sitting here writing the sound went away, then comes back 2 min later, has been getting worse lately. No color issues at all, so I'm not sure it's the colore wheel seems to be heat related? Can the color wheel become unbalanced to create the intermittent sound? Thanks a million for any advice.