CH - One radiator cooler than others

[syko89]

I've just moved into my first house this last week and looking for some advice.
The radiator in my living room doesn't get as hot as the rest of the radiators in the house.

I have a fairly old Worcester combi boiler (24i). There is no thermostat but all radiators have thermostat valves fitted.

Downstairs there is the boiler and two radiators (including living room), upstairs there are 3 more radiators.

For the living room radiator, I've taken off the thermostatic valve and the brass nipple goes up and down as it should. On the other side of radiator, the brass screw (check valve?) is almost fully open.
The radiator does warm up, but its only probably half as warm as the other downstairs radiator.

My CH knowledge isn't the best, so looking for advice on what I should be trying next?

Cheers

[syko89]

Thanks, I had tried bleeding it but there was no air.

I'll turn all the other radiators off and make sure this one gets hot. I'm hoping it's just the last radiator in the loop, so may need all of them balancing.