blocked pipes to 2 rads

[hotncold]

Hi all
Hope that u can help with this one.
Vented system in a flat (on one level) most pipework buried in concrete floor. No TVR's. 2 port valves , pumped system.
Problem is: 2 rads not warming up, think that these are off the main circuit (15m off 22m). drained/removed the 2 rads. opened each valve in turn.
water only gushes out of one valve per rad. the other valves only trickles out. The two valves (1 per rad) that seem blocked are the ones that used to get warm first when the rads heated up Ok. All other rads OK.
A couple of questions. I assume that its unlikely that two valves are faulty, so I suppose it is a blockage somewhere?
Is there any chance that I could remove blockage by introducing mains pressure ie if I connected to 1 valve, any chance it would come out the the other?

Any help would be appreciated.

 

[Breesey]

In any case you are really going to need to drain down.

The two 'trickling' valve are probably blocked, remove and inspect them - replace if necassary, Bob's ya uncle. Replace the others too while your at it! Refill system with a system cleaner and run this round for a week, drain and refill with inhibitor.

If there is a blockage in the system you could close the other rads and run mains through from the two valves you talk about, the water will come out of the vent pipe and take any blockage with it.

 

[hotncold]

Ok, I'll give your suggestions a go
Ta