I have an open system with header tank. Had problem in that upstairs rads worked continuously but downstairs were cold.
I have replaced the pump, but had to drain down the whole system first to do it.
I refilled the system, bled the rads. Opened the isolator valves either side of the pump. I then turned the heating back on at the controller and increased the thermostat.
The pump started no problem. I turned down the thermostat to stop the pump. I then bled any air out of the pump (large screw head in middle of pump).
Started again and left running, but pump sounds noisier that I thought it would.

My problem is that the heating doesn’t work!

I have used a hose to jet water via the 22mm outlet at the bottom of the header tank to move any air locks but still nothing.
The only time I can get any heat (or the boiler to fire) is if I have the pump running as normal and connect a hose to the drain outlet on the downstairs rad I used to drain the system. I figured it may push the air out having both ends open. (I also did it to make room in the header tank to allow me to use the hose to jet water in as mentioned earlier)

I can even hear the water rushing thru (I assume thats the sound) and of course when I try to bleed the pump its water that now comes out.

I can even hear the water rushing thru (I assume thats the sound) and of course when I try to bleed the pump its water that now comes out.

Hope this made sense??? Totally at a loss as to what to try next. Got to be an air lock but how the bleep do I get rid of it?

Thanks in advance

p.s. I am not a plumber but can usually do most plumbing jobs if its explained in plain basic idiot guide English (don’t tend to know the technical names for bits, tools or techniques)

Basics first did you fit the pump the same way round, there's an arrow on the body.

What if any motorized valves do you have.

Is there anair vent in the cylinder cupb.

Some details about the system, boiler etc would be good.

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Thanks for your reply...


Yes, double checked, all is exactly as the pump I removed


To the best of my knowledge, I don't have any (other than that switching one that is below the pump [not part of] to do with the flow I think)


The only "air vent" I know of is the overflow thingy that returns air/excess water to the header tank. When jetting the outlet in the header tank, I have also held my hand over the end to try to force the "jet" further in to the system, but no joy


Its a 30 year old open system in a 4 bed house (also 30 years old). Cylinder in airing cupboard where pump is. Boiler in integral garage (still the original, not sure of make/model etc sorry)

Boiler pilot is on, if I manually turn up the boiler it fires, but then goes back to pilot. My guess is that on a modern Gloworm boiler it would be an F22 error, insufficient water or air lock. In a modern closed system you would increase the pressure in the system via the top up taps in the airing cupboard until the pressure tank was up to pressure (1-2). This being an old boiler, it doesn't have any way of telling me an error code, but I guess it still has a self preservation system that won't let it fire if there's not enough pressure.

Also guessing, this could be why as I drain the rads with the heating on it gets warm. Boiler now thinks there's enough water/flow to heat it...sadly I can't be in the garage at the same time as draining the rads at the back of the house...possible water related accident

Absolutely freezing last night, kids very unhappy and difficult to sleep. PLEASE HELP! Not worked in a while so money very tight and can't afford a professional

hi marshall, sorry to hear you hav't worked in a while, firstly check the expantion tank in the attic, or it might be in the airing cupboard, I should have water in, if not the ballvalve is blocked,
if it has got water in, drain the system where you first drained it and check the tank again, if its still got water in, the cold feed is blocked, if its empty, its an air lock.

ok so check that and come back,

I am always surprised at how long it takes to bleed my 5 bed system from empty, I usually turn the boiler thermostat down so it does not try to heat air but CH room stat and DHW cylinder stat up to ensure the motor valves are in the open position and the pump runs to assist: I start by bleeding the highest and furthest radiator from the boiler, happens to be a bathroom (fitted a large bleeder to this rad and have a clear pvc tube to run into the toilet bowl, then i go around and tweak other radiators to help but it takes a while.
For the second part of tomplum's diagnostic check, you will need to tie up the expansion tank ball valve, otherwise it will continuously fill; to save draining the whole system you could drain half a bucket and check the level went down same.

just a note to aeromech, never bleed with the pump running, it will pull air in, to make sure your valves open, use the manual levers on the side,

Thanks Tom for the pump info, guess it causes cavitation but my old style Sunvic motor valves don't have an external manual override.

Thanks Tom. There have been developments since my last post so wasn't available to reply earlier...

We actually have a HomeCare plan thru our home buildings & contents.

Sadly, when I first had the problem of downstairs rads not working and the pump being RED HOT, they weren't interested 'cos we had some heat & hot water.

Now we have no heat or hot water they have sent someone out.

Def an air lock. Engineer Finally got most cleared by removing heat cut off sensor from boiler and boiling or "kettling" the boiler. When hot water streamed out of the overflow in to the header tank he switched heating off (therefore boiler) and bled rads again.

Had to repeat a few times.

During the last attempt, his boss called him & asked to speak to me. The insurance company had called him for an update; they then told him to pull his man off the job immediately since I wasn't covered for an air lock!!!

He was very appologetic, but said he won't get paid from that point forward so had to comply with their request!

As luck would have it (for a change), as we were talking, there was a lot of rumbling and escaping air and the engineer said "I think i've cracked it".

Sure enough the boiler now stays lit and we have hot water and heat to all but 2 rads (both downstairs). Engineer then had to go.

I've re-bled all rads but still nothing in those two. I will continue to run the system and try bleeding the rads periodically and hope it clears up soon.

I still can't beleive I pay for an emergency service who won't respond unless we have absolutely No Heat AND No hot water, and even then they won't get you up and working again if it something as simple as an air lock!!!

Steer clear of any homecare type insurance, especially if offered by ThePolicyShop (who are just brokers) since you are likely to end up with same cowboy provider that I've be lumbered with!

Thanks again for the replys and help, hopefully will be back to full working system soon

I'm already aware of these homeserve schemes, a waste of money, but luckily for you it worked,

what you need to do now is close all the working rads, and hopefull the pump will push the air to a bleedable point, don't forget, turn off the pump before bleeding

Will do, thanks Tom