2 rads not working (bled and balanced) any ideas

[jfk]

Hi I have 2 radiators upstairs in my house, running off a gravity fed heating system. They used to work untill recently.
I have bled them and there is water in both. I tried removing the rads and pulling water through each pipe using a hose untill hot/clear water came through, when I re attached the rads and filled them they heated up for about 5 mins then went cold.

The radiators did have alot of thick sludge in when removed and I flushed them through with a hose

COULD THEY BE BLOCKED Up?. I also tried shutting of the rads in the other rooms to force the heating their wayth no effect.
They are not trv's. Do I need new rads or is their something else I can try??
Cheers J

 

[jackthom]

Is the entire system gravity fed or is there a punp for the central heating?

 

[jfk]

Forgot to mention it does have a pump and that works

 

[jackthom]

The pump itself may be a bit sludged up and it's very likely the pipes leading to the dodgy radiators are too.

Is the pump set to max speed?
If so and that doesn't help, it might be an idea to dismantle it and see the state it's in.

If you do manage to get the hot water circulating through said radiators then that is the time to think about flushing and adding de-sludging chemicals to the system.

 

[jfk]

Thankyou I will have a look at the pump. When I had the 2 radiators of I did manage to draw a decent flow of hot water from both the flow and return pipes using a hose attached to the valves. Do you think running the system with system cleaner and then flushing through with clen water and replacing the offending rads will sort it?? Their is about 12 rads in total and their all very hot accept these ones.
Thanks again J

 

[jackthom]

The fact that plenty of water flows from both valves when the radiator is disconnected shows the pipes aren't completely blocked.

I would now concentrate on checking the pump and then trying to get even a little flow of hot water through these radiators with the pump (possibly a new one) set to maximum speed and the rest of the radiators shut OFF.

Once you manage that, it will be worth trying to force as much hot water with system cleaner around that part of the circuit as possible and then later moving on to clean and flush the whole system.

 

[jfk]

Hi, I ended up running some system cleaner through the system for a day then mains flushing it through the flow and return pipes on the offending radiator. I Removed the pump and checked for faults, replaced the 2 rads with new ones, filled and bled the system and everything works fine and alott more silent.