Hi Scotty,
I have a 2004 Nissan Sentra 1.8. Why are my brakes locking up in reverse?
Inspect them and see
What am I’m looking for?
Assuming we're talking about drum brakes, look for brake shoes being a bit crooked or worn funny. Pay particular attention to the raised surfaces where the shoes slide against the backing plate. That car is 19 years old and if those were never lubed (a typical oversight) they could be worn down. If that's the case the backing plate would either need to be replaced, or the contact points built up by welding and then ground down to spec.
things that might cause the brakes to lock up
The brake shoes are out of place and the master cylinder moves. When the vehicle is in drive, the brake shoe and master cylinder goes back to its normal spot.
