Radiators not all heating up

[brian62c]

Have just fitted a new ladder type towel rail in the bathroom, so drained down the system, and now only half the rads in the rest of the house are heating up.
System is conventional, ie not combi, oil boiler and header tank in loft.
Pumps appear to be working and rads have been bled individually. Also tried opening what I think is a system air vent next to the hot water tank upstairs (1ft vertical pipe) but barely any air came out.
Dave (gas4you) suggested a massive air lock in my related post of yesterday, which seems the most likely.
My only option seems to be to drain the whole system from the very lowest point (house is on three levels and I was draining to the lowest point of the second level previously) with the water supply left on into the header tank, to run water right through and hopefully clear it - but obviously that is going to be a pain and time-consuming.
Is this a wise move or does anyone have any other suggestions?

Cheers.

Brian

 

[no66]

Drain the system from lowest point for short bursts keeping one hand on hose pipe you will feel/hear air lock come through or run system until hot water begins to circulate for a while and then try shutting all good rads down and draining cold rads once again keeping one hand on hose pipe and wait for air lock and hot water to come through (assuming you have drain off's on those affected rads) .

 

[MANDATE]

A large air lock is difficult to remove because the air compresses instead of moving the water along. There is too much resistance.
When I had similar problem I removed the radiator and fitted a clear hosepipe first to one valve and run off a couple of buckets of water.
Then the same on the other valve. In fact I then coupled both sides together using the clear plastic tube, suitably fitted to connectors.
Running off the water through the open valves meant there was
little resistance and most of the air was released.
With the complete clear hose in place and system on I could see the water circulating and carrying some air with it, which meant it would gather in radiators and would require bleeding.
Once all other radiators were ok, the removed radiator was replaced.
Others may suggest applying a mains pressure hose to a low down drain cock to force water back up to the water tank and out through the overflow. A bit risky maybe?

 

[bengasman]

Provided your overflow is working fine, you could try filling the system through the drain cock. It often does the trick, but can make a real mess if you do it wrong as your loft is probably not designed to function as a swimming pool. Don’t blame me if it goes wrong. Would be a good idea to have someone watching the f&e tank while you do it. another way of doing it is to connect a garden hose to the vent pipe and give it a couple of bursts. Or set the pump on max, close cylinder and all radiators but 1. Run system until the one radiator is hot, close that one and open the next. And so on.

 

[meldrew's_mate]

Often the air locks are in the radiator return pipework. Suggest you remove the new towel warmer, attatch short hose to each pipe tail in turn, and open valve, collecting water discharged into a bucket - air entrained will be obvious.

Next try the air bleed above the cylinder again.
If the pump is on the flow side of the boiler (most are) then run hot water program only and continue to bleed at this vertical section until pump noise is constant (moving water, not air).
Then turn CH on, and at the upper floor close the flow valves to each rad, then bleed air from each. Open the flow valves and bleed again if excessive air gurgles into the rad (otherwise don't waste your time, do it later).
Work you way down the floors, get the system hot before final air bleeding.

Hope this helps

MM

 

[brian62c]

Wow! Thanks everyone for all the advice. As it turns out, repeated bleeding of all the rads in turn, plus turning the pump up to max, has seemed to do the trick for now. All rads now getting up to temp.
However, this little saga is not over yet - still feel the need to solve once and for all the loose fitting trv on the new towel rail - and as the lockshield valve on the return end is also seeping slightly from its turning head (?) when cold, I think it's past its best too.
So it's off to B&Q on the morrow - and another little job to be done at the weekend.
Ambition is still to finish this bathroom revamp before the tow weeks is up - but I'm not holding my breath.

Cheers.

Brian