Pump and Rad Problems

[Tim 72]

Hi all, I was wondering if someone could give me a little help.
I have an unvented ch system. Last night I decided to bleed 2 rads that were only getting hot to about halfway, the first bled fine but second only got a puff of air and that was it,could it be sludged up? Not sure.
Anyway this morning the boiler did nt fire up. I tried bleeding the pump and the upright valve in the airing cupboard and it got it going, the only problem is it runs for a short while (30 secs) then the pump needs bleeding again and so on.
I do nt know what I ve done but I do nt see how bleeding the rad could have caused this.
If anyone could give me any pointers it would be much appreciated.

 

[weareleeds]

Is it a sealed system? have you pressurised boiler? what boiler is it? etc etc etc

 

[Tim 72]

Hi. Yeah its a sealed system . The boiler is an Ideal Classic. Not sure how to pressurise the boiler, there is air in the expansion vessel located above it.