I am going to replace a stuck rear caliper on my 98 blazer. Will I need to bleed all 4 brake calipers or only the one I am replacing?

 

I believe if you put the end of the brake fluid hose up in the air after you disconnect it, there wouldn't be any way for air to go down into the hose and you'd only need to bleed that hose. Think about the plumbing of a sink or toilet. That curve in the plumbing drain keeps the waste air from coming up through your sink or toilet. Air rises, so as long as the end of the hose is higher than the rest of the hose, you should be fine.

It wouldn't hurt to bleed the whole system though, it is a maintenance item that should be addressed at certain intervals.

 

It may not be necessary to bleed the whole system, but as stated, it would be a good idea. You should bleed both rear wheels though.