Hot water working but Heating Keeps cutting out..PLEASE HELP

[ouch]

hello, i have a potterton 100e combi boiler that has been making some moans and groans recently, and today has partly packed in. the hot water works fine but the heating cuts out after only a few seconds, i took the front cover off and felt the pump was scolding hot.after turning the boiler of for an hour or so when turned back on the heating worked ok for a minute or so but the pump got hot once again and the heating cut out again.i have checked to see if the pump is siezed but it turns fairly easily. I bled the heating system and noticed black water from an upstairs rad.has anybody any advice where to start.please help!

 

[Agile]

Just a moment while I think!

Tony Glazier

 

[Agile]

It sounds as if you have little or no flow through your heating system.

Was it working within the last few days?

Are all the rad valves turned off?

Are TRVs stuck?

Is it sludged up?

Is the diverter valve stuck in the DHW position?

Tony Glazier

 

[ouch]

thankyou for the reply tony,the boiler has been off all night and day. i turned it on again an hour or so ago and it is all working again. i have noticed recently that the pressure needs topping up every week or so. could the system need a flush, with what and how would i go about that. many thanks mark......