How do i change the back brakes - 1989 Nissan Maxima

You need to bleed the brakes after you change any component containing brake fluid.

Check this link out. Check your master cylinder out,may be bad.Repair Guides Brake System Bleeding The Brake System AutoZone com

Bleed the system......Front and back...Good luck

You could have air in the system.
The rear shoes may not be adjusted correctly.

if something goes wrong with abs the brake system it reverts back to standard system!! If you can pump brake pedal up and hold it and start engine and it drops thats normal.You say low pedal if you go 15mph on road and check where pedal is when brakes apply.Power brakes will push aLMost to floor while stopped but while moveing you`ll almost go to slide or will go into slide if pedal is pushed to floor.Get on some gravel at 10 mph and hit brakes to a complete stop get out and check to see if all 4 tires slid or 2 front or only 2 rear. this will get you closer to problem good luck.

change the brake hoses going to the calipers. these hoses deteriorate from the inside and clog up not letting the fluid back out of the calipers. there is also one for the back brakes I recommend to replace this one too.

the rear brakes need to be changed, the parking brakes are always the rears.

its more or less and backing plate you can drive without it it keeps brakes cool and gravell free > speaking as a tech you should replace it?

does it have rear disc brakes or drum brakes, if disc brakes should be changed just like the front and you might have an emergency brake shoe inside the rotor that they call a halo shoe, if it is drum brakes take off the adjusting spring and the return spring remove the brake adjuster,the the brake bar then remove the brake shoe hold down spring by holding the pin from the back and pushing and turning the spring to remove from the pin, you might have to remove the the emergency brake bar from one shoe by removing the horseshoe clip from the pin on the shoe if you have problems putting it back together look at the other side that you have not torn down yet.

Do you mean back brake pads or the back brake callipers?
To change pads you need to use a rear brake pads changing tool to screw in the calliper piston or if you are experienced enough you could screw in the calliper with a two mm thick piece of metal sheeting that fits into the grove of the piston.
If you need to replace the whole calliper remove the hand brake cable first and clamp the flexible brake hose remove brake hose, remove the callier with cylinder and then remove the calliper holder. fit new holder pads and locks and the calliper with the piston and the brake hose and the hand brake cable. Bleed the brakes. Mike