Hello jeep enthousiasts.
I have had problems getting heat in my Liberty 2008.
I have:
Changed the thermostat
Flushed the entire system back and forth with a garden hose 3 times
Bled air from system completely everytime
Blend door actuator works fine and I also have manually moved the blend door til it hits the stoppers both ways. I can hear the pressure and sound of rushing air change when I move the door by hand or with the actuator.
The heater core does not leak.
I have done a leak test with a pressure pump and gauge at 20psi for over 30 minutes.
The hose going in the heatercore is warm but not hot the one comming out is lukewarm.
There isnt much flow in the heatercore hoses I think, even though the heater core isnt plugged because I can run a garden hose through it

 

I have a similar problem on a vehicle that is not a jeep but one vehicle is much the same as another in how the heater works. My guess is that the thermostat is opening early, it might be a new one but they all relay on a blob of wax to operate and can be wildly inacurate, new or otherwise. I once changed three or four thermostats on one vehicle before I found a good one (price has nothing to do with quality)

 

Sound like a new waterpump may be in order. The Jeep uses a plastic impeller & can get damaged if wrong coolants are used.
Only Hoat or Zerex G05 should be used.
Also if the thermostat was staying open or early, it would set an engine code, too long to warm up.