3 radiators not working

[HavingANightmar]

Hi,

I have recently bought a new house which has a pressurised gas heating system. 3 of the radiators do not work.

I have bled all radiators and pump.
I have taken radiators off wall to checked for sludge (very clean water)
whilst radiator was off I checked the Thermostatic valve worked and also the normal value on the other side. these worked as expected (paid plumber also replaced these to see if that would resolve my issue).
I have turned off all radiators in the house except one of the 3 radiators that are not working (and repeated for other 2 radiators)
I have connected a hose to the radiator to check flow

this suggests a blockage but its unusual for pressurised systems to get blockages.

any ideas?

 

[jonnyswamp]

Are the affected rads all on one floor, maybe zoned seperately
If so, look for another room stat on that level which will be wired to a 2 port valve which will open when stat is turned up
Need to know more to give an accurate answer
Details of the system?

 

[jtsplumbing]

As (jonnyswamp) says and just to add it's NOT unusual for pressurised systems to have blockages, what size pipes are feeding your radiators ??

 

[Best]

Turn all radiators fully off except one of the rads that doesn't work. Also turn any separate bypass valve or valve to cylinder coil off.
Open up one valve at a time into a hose while keeping the system topping up. If both valves keep flowing then you don't have a blockage if filling loop is at boiler. The route between boiler and rad would be clear.
A standard radiator valve - like a lockshield, can be faulty and let the flow only in one direction due to the 'washer' part being loose and pushing down with flow. But this will be unlikely with 3 rads