1999 Ford F-250 Super Duty Q&A

1999 Ford F-250 Super Duty Question: Heat is not working I put a new water pump on and a new thermostat?

I seem to be losing coolant slowly but I can't tell where, but heat still doesn't work after I refill coolant. Another symptom is normal temperature while running but gets hot when at a idle. Any suggestions would be appreciated. -
Answer 1
POSS LOW COOLANT LEVEL -