Could be blocked or the micro bore blocked. You could try putting some system cleaner in, and see if that helps. If not a drain down and remove and check manifold.
Could be blocked or the micro bore blocked. You could try putting some system cleaner in, and see if that helps. If not a drain down and remove and check manifold.
Well I never realised these manifolds have two chambers, one flow and one return, there was a slight blockage in one outlet, just enough to stop hot water reaching the rad.