Radiator problem groundfloor

[GTMS]

My radiators from the ground floorx2. Always works intermitt. If I close the valves from the rooms at the 1st floor the radiator would start to warm, if I open the radiators from the 1st floor the ones from the groundfloor would stop to work. What that can be. All the TMV valves were replaced but the problem still the same. I friend of mine toldme that this can be a air lock. But why the radiator from the 1st floor always works?
I tried to bleed all radiators and the problem still the same.

 

[buster52]

It could be that its all the radiators are fed buy to small a pipe size and this one is being starved of flow.
let the whole system get cold turn on the heating and go round the system and check which end of the radiator gets warm first (you will be able to check the one thats not working when you get some flow to it), first go to the radiator thats not working and make sure both valves are open, then start with the hottest radiator's close the lockshield valve all the way and then open half a turn if the thermostatic valve is on the cold Or outlet side remove the head and there should be a plastic insert with a slot in it which can be closed to reduce the flow if the radiator starts to get to cold open slightly go round the house doing this to each radiator in turn until you get a supply to the rad thats not working if this does not work then you probably have a partly blocked pipework, this is an old fashioned way of balancing the radiators you can do it with thermostats strapped to each pipe on radiator being adjusted or a digital thermostat.
when you have finished monitor each room and adjust the lockshield valves to increase or decrease the flow you will soon tell if you are getting enough heat to each room,
another possibility is a worn out pump if the heating has worked well before and the pump is getting a bit old it might be running but not working fully in wich case replace it
hope this helps a bit