Hey there everyone ! My name is Edgar and I have a 96 D1 300tdi, auto , EDC

I've been having some overheating issues lately, decided to remove radiator and found it was pretty damaged , replaced and now having trouble properly bleeding or so I think.

Things replaced within last year:
Head/gasket
Water pump
Thermostat
Expansion tank
Radiator
Heater core
Viscous fan

I also pressure tested the coolant system and found no leak. Did a sniff test as well and tested clean .

The issue I'm currently having is no heat inside cabin which makes me think air lock somewhere. After installing the new radiator I filled with distilled water to test the system , everything was working fine , I had heat inside the cabin, before thermostat even opened. Engine got up to temp, thermostat opened as it should and seemed coolant was circulating as it should.

So then I drained the system again and filled with proper 50/50 coolant mix. After that I haven't been able to get heat inside cabin before or after the thermostat opens which again makes me think air lock somewhere.

Have tried all sorts of bleeding techniques, elevated expansion tank, on a steep incline , tried the coke bottle trick and that seemed to release some air bubbles but not enough .

Anything I could be missing or haven't tried ? Any guidance is much appreciated.

Remove rad top bung
Remove bung on top of stat
Fill coolant tank until fluid comes out of rad bung
Refit rad bung
Keep filling header tank until you are at correct level
Refit header tank cap
Carry on filling coolant through the stat bung until full
Refit stat bung and roadtest until to temperature