read the forums still no joy

[crapheatingsystem]

ive read all the answers to the cold radiators down stairs syndrome,and ive tried everything and im totally baffeled.all rads downstairs cold.some on the old micro bore plastic some modified onto 15mm bore plastic still nothing all except 2 rads have the trvs.bathroom rad has 15mm copper pipes in and out not trvs as was told this is a safety feature so no over heating??? shower room towel radiator no trv fitted.system had been quite sludged up and been flushing and draining for a few years,very acidic water up here in highlands.had all rads off and flushed etc.dont think its a pump prob as its running at speed 3 and if i remove a valve down stairs water blasts out and gets hotter and hotter,but as soon as you fit valve back on nothing.

any ideas folks.sorry to say all local plumbers and ive tried em all absolutley clueless.

tried the vave balancing etc
ian

 

[seco services]

sounds like a blockage on the main flow/return to downstairs rads.

 

[crapheatingsystem]

sounds like a blockage on the main flow/return to downstairs rads.

thanks for that.does it sound feasable what ive described,some times the rads are luke warm down stairs,if its a blockage on the return circuit where do i start.as far as i can see just 2 pipes lead out of the boiler(mtd outside oil fired camray),they go up to copper tank from tank 2 pipes out,under first floor and branch off to feed all upstairs,i then assume somewhere,they go down to ground level to feed the downstairs ones,so the pump has got some pretty hard pumping to return the flow back up to the tank and around.ive found some small micro bore pipes that drop down to some of the rads down stairs they dont seem hot in or out,yet take of the radiator trv and turn up to hot it gushes out scalding water?
ian