Pulling my hair out ....vented central heating system

[norfolkinesox]

Hi,firstly a bit of history,I have a back boiler which works fine however I'm struggling with downstairs radiators getting remotely warm,to date I have replaced the pump as before I had tried balancing system to no avail and now have removed both radiators downstairs as possible sludge may be the issue,I drained the system fully flushed both radiators out and not really much crap came out of them.
I've fitted new vaves on both radiators as one started to leak so as a precautionary measure replaced them all,I've refilled system added inhibitor and bled them from downstairs up.
I still have the problem of radiators not getting warm,first will it take a while after refilling for it to get hot ?just the pipes coming from upstairs are hot and get gradually cooler approaching the radiators with the radiators not getting hot at all,all upstairs are hot and I've left them open only half a turn on outlet of each radiator.
I believe maybe a blockage but they bled fine,I'm lost now

 

[Agile]

What about hot water?

Is that pumped or gravity and is it working?

Sometimes a non return valve was fitted and they sometimes get jammed.

All this talk of flushing but no indication of how it was done, or by whom and what chemicals were used?

Tony

 

[norfolkinesox]

All radiators are hot up stairs I've shut them off left heating on to just downstairs and the pipes are red hot radiator only just noticably warming,even though I flushed radiators in garden with hose pipe and mains pressure could I still have an issue with radiators,am I looking at buying new ones as they are older than ones upstairs but both can't be b
Coked or should I say restricting flow

 

[norfolkinesox]

What about hot water?

Is that pumped or gravity and is it working?

Sometimes a non return valve was fitted and they sometimes get jammed.

All this talk of flushing but no indication of how it was done, or by whom and what chemicals were used?

Tony

flushing was just with hose in garden and mains pressure,as it was just the two rads downstairs that wasn't working,I have hot water but must admit when I have hot water and heating selected sometimes the radiators don't get hot even upstairs (is hat an issue with 3 way valve?)'

The radiators downstairs are starting to get hot very slowly with upstairs rads isolated,which I thought would be balancing yet I've tried all that,I'm either really thick and missing something it dont make sense

 

[norfolkinesox]

Well the radiators downstairs are now hot,and in the process of opening up one at a time of the upstairs rads to see when I lose heat downstairs,got a feeling I will at sometime

 

[Agile]

Has anyone ever made any attempts to balance the system?

Tony

 

[norfolkinesox]

Thanks for reply Tony,I tried that initially with no luck,at minute I've had downstairs hot with upstairs rads off and I've opened three out of four upstairs now and downstairs now struggling,balancing I shut off all rads opened inlets and only opened out let's quarter to half a turn this didnt help with downstairs,and to be honest up stairs didnt get real hot so opened them up slightly more,is that right?
This is why I thought it was maybe flow so fitted new pump ,others also suggested it

 

[norfolkinesox]

Radiators up stairs were red hot so gagged back outlets to direct more flow downstairs the downstairs feed pipe got real hot rads only mildly warm but upstairs lost some heat( gagged back outlet to balance system) I'm at a right loss as it seems system can't cope yet pumps new(off eBay brand new in box) but something tells me it's the pump any ideas so frustrated with it now
Pumps on setting number three as well