The following is how to clear the cache partition on the Galaxy S4. Only do this is you are having a problem with an app.

  1. Turn off the phone and remove the battery, then reinsert
  2. Press and hold the Volume Up key and Home key, then press and hold the Power key
  3. When it vibrates release the Power key
  4. The recovery menu should appear - release the other keys
  5. Navigate using the Volume keys to Wipe all cache (power key to select)
  6. Press the Power key to reboot

See More: Clear cache partition on the Galaxy S4