Hi was wondering if anyone could help, i have a combi boiler located in the cupboard upstairs. all upstairs rads are really hot but the 2 in the living room are cold. i shut the valves off and removed the rad, blasted the rad thru with water and its perfectly clear. i then opened the t r v and only got a slight trickle when draining down yet when opening the return there was a good flow until system was empty. i replaced the t r v and refitted rad and filled system. i left both vales shut on rad then i opened the flow and bled air, rad got hot until i opened the return valve. could this be a case of a restriction in the flow pipe to the rad and how cud i romove it? wud a chemical flush sort this problem out? Thank you Chris.