If your system is sludged bad enough to cause those problems with hot water it may not be repairable without replacing the secondary heat exchanger. best thing to do, other than getting a profesional powerflush done, would be to add some system cleanser to the system such as sentinal X400, or fernox, and run the system for upto a month then fully drain down and refill. if there's no apparent drain off on the sytem you may need to remove a radiator and do it from there.
andy gas man
April 2009
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