I recently had to replace a rad. Since then a different rad has been cold one day then it works fine, but another one has gone cold! I have bled the system and all rads are full. Could debris have gotten into system and be blocking the valves before being pushed on into the next? Is there anything I could
add to the system or should I drain it down completely??

Ann, January 2007

would say its more like airlock in the pipes, your rads may also need balancing

hi-spec plumbing, January 2007