2 out of 4 rads upstairs hot all downstairs cold.

[madsreece]

turned the heating on the other day as usual but found no heat going to the rads, plenty of hot water from taps though. called a plumber basically did a few checks etc said it was a blockage but was pretty vague, drained a few rads, but upshot was, he left and i have only two rads working in the bathroom and hall landing both which are near the upstairs hot water tank, and pretty much above the downstairs boiler. all the other rads are cold. i drained a couple of downstairs rads and they started to get warm, but then went cold again. any ideas

 

[ChrisR]

Sludge. You need a powerflush. If you know what you're doing you can shift a lot of it with a mains hose.
If you don't you'll get floods.

 

[brumylad]

check the pump is working.

how old is the system?

is it sealed (e.g. combi boiler) or is there a header tank in the loft?

 

[madsreece]

thanks for your replies, however found the problem, i need to replace the 3 way motorised valve activator, all my rads are now warm as the setting is now on manual until i can get it changed. for your info brumylad, i have a header tank in the loft, the system is fairly old but the boiler and hot water tank are a year old. pretty certain the a powerflush is not needed. but thanks for your input.