Cold radiators, at the bottom NOT the top

[hthebrave]

I have an eight radiator, two pipe system running from a Vokera 80SP. My problem is that all the radiators are cold at the bottom and hot at the top. I have tried bleeding but as there was no air in system this hasn't helped. Am I overlooking something simple ? or does this signify something more sinister. I have checked the pump, by switching system off then restarting and feeling motor for vibration. I'm sure this happened not long after installation, 10 years ago, but cannot remember the solution.
Many thanks in advance.

PS just had the hot water diaphragm replaced last week could this have anything to do with it ?

 

[Nige F]

10yrs sounds like sludge.....powerflush required . Take one rad off and have a look at the amount of black crud in the bottom.replace and if that one`s ok.do the rest,or get an engineer in ....Brit Gas are the dearest, so get some quotes Could be the pump is tired and not circulating properly...cheaper to DIY check a rad first.