I brought my LeEco S3 two weeks ago. It is a decent phone for only 150 bucks(130 if you got it during the black Friday sale). However, it comes with not one, not two, but three video app and they all have services running in the background. I tried to use the tool on XDA to unlock the recovery and it doesn’t work. Then I found a tool on a Chinese website and it worked for me. Hope this helps you guys.
- Go to Setting-About phone. Click Build Version about seven times and you will be in Dev mode.
- Go back to the system settings, click the developer options at the bottom of the page.
- Turn on the Developer options, then turn on the OEM unlocking and USB debugging options.
- Connect your phone to your PC, make sure your computer recognizes your phone.
- Turn off your phone, wait till the screen is completely off. Hold Power and Volume down button to enter the fastboot mode.
- When the phone shows you’ve entered fastboot mode, open my toolkit and choose the option  to unlock your LeEco S3.
- After the phone is unlocked, choose option  in the toolbox to flash TWRP Recovery.
- If the flashing process was successful, the phone should automatically boot into the recovery. It might show Mount-Decrypt Data and ask you for the password. Just click cancel. Then change display language to English(default is Chinese) by pressing the button at the down right corner of the screen(above the slider)
- Swipe the slider to allow modification to your system partition. Then go to Advanced-Tools.-Root Device to root your phone. You can also unroot your phone from here.
- If the process is successful, you will see SuperSu is installed on your phone. However, it is a cracked pro version and the English language pack for the app is missing. Just delete it and redownload the SuperSu from the Google Play Store.
- That’s it! Enjoy!
USE AT YOUR OWN RISK!