I have a Sony Grand Wega 42

More than not your scirocco fan that sits right above the lamp is at fault. This is not an uncommon failure and it can be a blessing in disguise as these fans are designed poorly and often clog with so much dust/dirt they are really doing no cooling at all. My suggestion is to NOT use the TV until you have it looked at. If you leave it like this too long chances are you will start seeing warping on the lamp door and the surrounding plastic. It can also cause the thermal fuse to open up rendering the set useless until repairs are done. Mind you this is NOT a fire hazzard but one that should not be ignored. There is a modification kit for these models to replace the fan with wider slots on the fan and then to relocate the thermal fuse to below the fan instead of its current location above it.