Can a hemorrhage occur after death?
Usually,blood moves through the body by force from the contraction of ventricles, the contraction on muscles, gravity, or other forces. At death, the only force left is gravity, which is why we see lividity (or livor mortis -pooling of blood in dependent positions) after death. This continues for ~8-12 hours (depending in part on temperature). 

The blood in the arterial system at the moment of death is still under pressure because arterial wall musculature has not relaxed yet. (I don't know how long this takes, to be honest.) If an artery is pierced (say, a bronchial artery, e.g. by a knife), blood will flow from a high pressure area to a lower one (e.g. into non-inflated lung tissue, the abdominal cavity, or the outside or the body) So post-mortem hemorrhage can occur until the arterial musculature has completely relaxed. After this relaxation, stabbing a corpse will produce a small amount of oozing at most, unless pressure is applied somehow, e.g. during CPR. CPR may make small petechiae larger.

Livor mortis can occur in the lungs post death as well. 


  as the blood accumulates in the dependent areas, the pressure of the settling blood can rupture small vesslels, with development of minute hemorrhages (petechiae)... This usually takes 18-24 hours... and is more common in (asphyxia).


Hanging is death by asphyxia, and is known to be associated with lung hemorrhages, but very small ones.

Forensic Pathology, Second Edition By Dominick DiMaio, Vincent J.M. DiMaio, M.D., pp.22-25