My rear brakes are snatching and making a loud grinding sound when i try to stop. I have replaced the drums rotors brakes and brake lines but still have the problem of my brakes adjusting out on their own. i'm not sure what the problems is i need help?

Worn brakes

I suggest you pull rear drums or have someone qualified look at rear brakes. it could of broke a spring or other brake hardware. I suggest stop driveing the car until you can inspect or have the brakes inspected..

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Most people do not remove the rear rotors and inspect the Emergency Brake shoes. These often peel off the metal backing on the shoe and jam inside the interior Drum of the rotor. Some people will hear a rusty grinding noise after pulling away from a stop.

These brakes have the old "star-wheel" adjusters and may need to be adjusted more loosely to remove the rotor. Its a bad system in my opinion; the drum always rusts and corrodes and the Ebrake shoes are banana peel thin. With corrosion, the drum acts like a grinder and chews up the brake shoes. Some other configurations use a mechanical link on the caliper to make the service brakes act in an Emergency. It will override a hydraulic failure, but you still need good pads on the caliper.

Yes.
Please find someone who will remove your wheels and check your brake drums or rotors, whichever you have, and do this out of kindness.
This person need to show you the rotors inside and out, and if you have brake drums on the rear, remove those and show you the insides.
You are looking for metal-to-metal area that will make a grinding sound.
It will be easily seen by you. especially when you compare that with a normal smooth wear area.
If you find a rotor or drum NOT smooth but all rough, that is the wheeel you need to have fixed.
One more thing. I have a Honda Civic that grinds most every time I stop the car, and there is nothing wrong with it.
Some brake shoes and rotors are noisy.
Be blessed.

air in the system wont make the brakes grind,you have done some thing wrong there.

The grinding sound when braking is almost surely worn brake pads. If an abs sensor is bad it will set the abs light on. Heres an easy way to figure whether to look at the front or rear brakes first. When braking, take notice as to whether the vibration is felt more in the steering wheel or the seat. If it is more in the steering wheel take a look at your front brakes first, and obviously if it is felt in the seat look at the back brakes first. Both front and rear need to be checked out because the pulsating you are feeling is due to rotors or drums that have been heated up and warped. In order to fix both problems, you most likely will need brake pads and rotors/drums. If you just replace the pads, not only will the pads wear away faster due to the damage to the rotors/drums, but your vibration issue will not go away and infact may intensify.

The grinding noise probably means you need to put new brakes on. If you fill the brake fluid reservoir, and then change the brakes, the new fluid will run out anyways, because the new brakes will have to be put in, and the fluid will run out.

Check your brakes ASAP. When you hear a noise like that the brakes are usually already shot. Check them and you may needf machine work done or have to replace the drums/rotors. When I say about checking the brakes check the front also even thiugh they are not grinding they are working harder to stop the car since the rears are grindinding.

Sounds like your brake pads/shoes need replaced. When the brake linings wear out, you have metal to metal when you step on your brake pedal. You may have to replace rotors/drums due to severe scarring.