radiator is cold at the bottom hot at the top

[Hawkwalk]

any ideas what may be causing it?

[thedogwalker]

Air in the radiator, it needs bleeding.

[Hawkwalk]

I thought if it was air then it would be cold at the top and warm at the bottom.

[grasscarp]

Answered on this website - sludge
http://www.diynot.com/forums/viewtopic.php?t=7 2790

[buildersmate]

Agreed. There is sludge around the middle of the rad, which naturally sinks to the base.
Hot water is getting into the rad but can't circulate properly across the rad and is just flowing upwards towards the top (it will naturally do this anyway because hot water is less dense than cooler water).
It has the overall impact that you describe.

[Hawkwalk]

thanks for the answers

[tezestwing]

follow bathjobby for your remedy and put lots of waterproof sheets down all over your walk rout with the radiator tails uppermost( best cling film round tails before moving) one little drop on to the carpet will spell disaster oh and when you re fill you only need one valve open just a little to start with to make sure they are sound of any leaks with heating OFF then when full of water adjust valves back to pre noted positions hthTez