I have an S3. My phone is burning up. It's hot. The battery has drained from 100 to 5 in under 90 min. I installed a task manager to close background apps and an app to clean unwanted processes. It's only a year old, the phone and battery.
Hello. Welcome to Android Central.
I would uninstall the task manager and cleaner apps.
Have a look at the Battery and Data Usage graphs to see what is taking up the most resources. Try also the GSam battery app for better info on Apps and temperature.
Go to Accounts - Google and other accounts, with Sync on, to see if there is a red sync error showing.
If the battery has bulged, try spinning it on a flat surface, you probably need a new battery. It will still help to track the causes of the drain and heat.
You can post screenshots (power and home button) of the graphs and someone can take a look.
http://forums.androidcentral.com/showthread.php?t=413366