Radiator - Cold Spots

[Classic]

The rads in my parents house have cold spots.
I have 'bled' them but there is no air to remove. A plumber has said it is due to build up of sludge in radiator.
He recommended:
1. remove rads and washout to remove sludge
or
2. Use a pump to remove sludge

Has anyone had this problem, how was it solved and what was the cost?

 

[gramlab]

Had the same problem myself - you would be surprised how much crap can build up in them. Drain the system (low point). Take each rad off and pop a hose in one end and wash it out. Its a dirty job ..... Enjoy