radiator not warming up to temp

[nivek24]

About 3years ago i replaced the room radiator with a new one.
i took the opportunity to place the new one on a different wall, so had to move the pipes. I followed the inlet and outlet using new plastic piping.
Since then it has not got hot like the other ones in the house.
Last year i had a new worster boiler fitted, but still it does not get hot. Today i removed the radiator thinking it may have a blockage in it. I left it outside with a hosepipe running through it, the water flowed straight thru no problem, just a slight discoularation of the water, flushed it from both directions all clear.
I refiited it, bled the system, problem still the same.
The feed into the radiator has a thermostat on it, i removed the top of the thermostat thinking this may have been faulty, still same. THe feed pipe into the radiator is hot, but the one out of it is only luke warm?.
The radiator gets warm at the top, bottom cool, but not the full length of it its like pockets. The radiator size is 79" long,12" high. double
I have a drain on the outlet side of the radiator as this is the furthest from my boiler.
If i close the inlet into the radiator, i can open the drain valve on the outlet and water flows out ok.
i can't think what else to do without taking my floor up and checking the pipes.
Thanks
Kevin

[collectors]

Its likely the system needs balancing. 1st turn all the TRV,s off with the exception of the rad that's not getting hot, & make sure this rad now gets up to temperature. If yes! turn on all TVR's & find the hottest radiators in the house & turn down the radiator valve on the other end of the rad (Opposite the TRV) buy about 1 to 1.5 turns to reduce the flo to that rad. Do this on a few of the rads & see if this pushes the hot water to the problem rad.

[nivek24]

spot on mate, i did what you said and radiator warmed up ok.
Great. Thank you Kevin.