Luke warm radiator

[woodchopper]

The main bedroom upstairs in our house we split into two with a stud wall and had a plumber install a new radiator ( small single conv. ) in the second half - since then I can't get much heat into the new radiator.
I have tried turning down the balancing valves in the radiators downstairs and the others upstairs to "push" the water into the new radiator so far that the downstairs rads are nearly off themselves
( about a 1/4 of a turn open ).
What else can I do ?
I can't turn the downstairs rads off any more or is a it a case that the circulating pump is not sufficient.
I have bled all the rads and there is no air in the system.
The only diffence being is that the existing rad in the "old " room and the new one have both now got thermostaic valves fitted.
There are only 2 double conv. and 7 single convs. in the system. The new rad is only luke warm at the top and cold at the bottom.

[deggers316]

check that the valve at the other side of the radiator is turned fully. open it's usually got a cap on it pull it off. use small spanner or pliers to check its open fully

[woodchopper]

It is.

[vignon]

Get the plumber too return and sort.
Or undo the pipes one at the time ie:-turn the other side off and see if any water comes out if not it could be blocked with muck, poke knitting needle or wire too dislodge.