Volvo Repair: Water Pump Volvo 1995 850, head gasket, initial reason

Question
I have replaced the radiator, thermostat and now considering the water pump.  After replacing the rad and thermostat, I let the car run for twenty minutes and the rad fan comes on, so I ruled out the rad fan, however the water in the reservoir begins to boil.  I don't see any water being pumped out of the reservoir while the car is still running.  Can't say, that I have noticed any leaks on the ground from the water pump as I have been filling the reservoir and it boiling over at times.

Answer
  Greg, what was the initial reason for the heating system work? Pumps "usually" leak before they fail. You may be looking at a bad head gasket?
   Be sure you have the system properly bled cold, before proceeding. Use a pressure system to force all air out.

Mark