04 350z my left rear brake locks up don't know why?

 

Heh, I'm actually fixing that problem of mine today. Ended up having to buy a new(re-manufactured) caliper.. Anyway. How many miles are on that caliper? Do you drive the car often(at least once a week)? Have you had to stop suddenly recently where you had to mash on your brakes? Did you recently have them serviced? IF you don't drive the car often, do you keep it parked outside in the hot and humid Caribbean weather? I've been to the Virgin Islands. I know how humid it is.. Just trying to get a better picture from your one sentence..

 

Could be any number of issues like Atreyu said.

I had all of mine lock up from being parked all summer. Was due to rust build up. Just needed to be broken free and cleaned.

But if it's happening due to driving it could be in need of a service or your ABS is going out.

Answering the questions above should help us track it down a lot easier.