2004 sentra overheats, new waterpump and thermostat. no heat out of heater. is there a second thermostat?

Are you sure there is not a air pocket in the engine after changing water pump,
there is only 1 thermostat

This happened to me on the 2005 nissan sentra...i had the thermostat and water pump replaced, the mechanic continually tried to remove any possible air pockets as the problem continued...it turns out there was a problem with the head gasket, it was repaired and thankfully did not need replacing otherwise the cost would have been more significant, the mechanic also replaced 2 of my spark plugs, he told me it's not an easy problem to diagnose...good luck

Here are a few things to try. Check to see if the electric raditor fan is coming on after the engine gets hot. If not, this could cause your overheating problem but it wouldn't explain the problem with no heat coming out of your vents. I'd also check your antifreeze level. If it's too low it would cause you car to overheat and you wouldn't get heat out your vents. I'd also check to make sure the thermostat was installed in the correct direction. If it was installed incorrectly it could be the cause of both of your problems. If you bought this car used I'd check to see if someone bypassed the heater core with a hose. Sometimes this is done as a temporary fix for a leaking heater core. This would explain no heat coming out the vents but it wouldn't explain the overheating problem. Maybe the 2 problems have separate causes. I hope at least one of these suggestions helps you out.