radiators cold at bottom- hot at top

[campag0]

Upstairs I have 4 radiators,2 in bedrooms and 2 in ensuite bathrooms.The bathroom ones are uniformly hot but the bedroom ones are only hot at the top half.All the radiators on the ground floor are ok.I have a combi system with a new boiloer but I had this problem with the last boiler too.I have removed the bedroom rads and flushed them out but it made no difference.
The water pressure and the output boiler temperature is ok.I called out a plumber but he did not have an answer.
Any ideas?.

 

[bennythedip]

How did you flush out the rads ? If you just stuck a garden hose on them it won't shift too much if they're badly clogged up.

 

[AWheating]

whats the room temps like? could it be thr trv shutting down the rad when the room had reached temp?

 

[campag0]

The rads were powerflushed.The room temp is not warm and I checked the trv which is working fine.The hw inlet pipe gets very hot and just under the rad inlet is also very hot
.I turned off all the rads downstairs but there was little ,if any difference to the upper rads..
Does anyone think that the 10mm supply pipes to the rads could be blocked and cause this type of problem?

 

[PlumbBobBob]

when radiators stay cold at the bottom whilst being hot at the top this points to a sludge problem imho

 

[AWheating]

is the lockshield valves fully open? how did you test the trv?