Radiator bleed not working…screw broken?

Courteous

Hi folks,

hardware and DIY newbie here, just trying to bleed my radiators (first time I’ve tried this). Things aren’t quite going as smoothly as the YouTube demonstrations and I’m stuck. I’ve an idea of the problem and a workaround but not for certain. Hoping MSE forum can help. 

So…the bleed valve (not sure if that’s the right word) on the radiators comprises a screw with a slot head, surrounded by a plastic part (pinhole in this - maybe where the air comes out?…) backed by a metal nut. The screw heads on all the radiators are all quite mashed up -they look like they’ve been attacked - but I have a tool that fits and can turn the screw on some of the less mashed ones. I bled one radiator fine (hurrah). However on the other 2 the tool fits, the screws will turn, and the plastic parts turn too (these will turn by hand in fact) but nothing else happens. 

I’m wondering if the thread/groove where the screw fits are messed up somehow.

My question is: would it be okay to just turn the metal nut, using an adjustable wrench? I’m presuming this would let the air/water out if loosened enough but don’t really want to experiment. 

Any thoughts guys?

grumbler

I think it's OK to do as long as you don't get close to the position  when the part disconnects from the radiator.

ETA: you can replace the valve. If the radiator has both TRV and lockshield valves, you can close them to avoid draining the system.

FreeBear

Courteous said: So…the bleed valve (not sure if that’s the right word) on the radiators comprises a screw with a slot head, surrounded by a plastic part (pinhole in this - maybe where the air comes out?…) backed by a metal nut.

Sounds very much like the Kudox radiators that I have here (without the chewed up bleed screw). You can get spare plugs that should screw straight in. Self bleeding plus also available. A couple of examples -

https://www.screwfix.com/p/radiator-vent-blanking-plug-nickel-2-pack/40972

https://www.screwfix.com/p/aladdin-hv30c-autovents-chrome-2-pack/34093

Other brands & suppliers available.

If you close off the lockshield, put a mark on the stem & body and count the turns to close it off. Make a note and tape it to the side of the radiator.

Courteous

Thanks both, 
I just wrote a response and was just about to click send when my phone died….noooo! 

The whole part looks exactly like this:

https://www.amazon.co.uk/MANUAL-RADIATOR-VENT-BLEED-VALVE/dp/B007JX6CVM

Thanks for your thoughts. I’ll ponder anon and check re TRV /lockstep valves. If I could replace the whole part if I had to, without having to dismantle anything that would be nice. I honestly didn’t think of that - my mind went to trying to manually reconstruct the screw/thread (don’t even know if that’s possible!). 

Puzzled as to why on 1 radiator when I (accidentally) removed the screw entirely there was no hissing of air/water but I’ll leave this gripping mystery for another time - surprised to see it’s gone midnight. 🤘🏻

Over and out. 
 

FreeBear

Courteous said: Puzzled as to why on 1 radiator when I (accidentally) removed the screw entirely there was no hissing of air/water but I’ll leave this gripping mystery for another time

It is a very small hole behind the bleed screw - Easily blocked by a bit of gunk.

If you are feeling brave, you could try taking the plug out and see if the hole can be cleaned out with say a small sewing needle.

Norman_Castle

"However on the other 2 the tool fits, the screws will turn, and the plastic parts turn too (these will turn by hand in fact) but nothing else happens. "

Have you tried holding the plastic still while undoing the bleed screw?

Section62

Norman_Castle said:

Have you tried holding the plastic still while undoing the bleed screw?

The plastic part usually rotates freely and independently of everything else - it is only there to guide the water to a point where it can easily be collected, rather than spurting all over the place as the old ones sometimes would.

If it turns when the bleed screw is inserted and turned it probably implies only that the external diameter of the tool is slightly too big for the assembly the OP has.


I would go with FreeBear's answer - that the vent hole is blocked by debris.  Or possibly, that the radiator valves have already both been turned off.

Or if the OP's system is unvented there is a small chance the system pressure is too low to allow anything to come out of the bleed valve.

Personally I'd take this opportunity to replace the chewed up screws, then check the radiator valves are on and there is pressure in the system/water in the header tank.

Courteous

Brilliant - thanks for the input. Feel a bit less stuck/closer to identifying the problem/s and solution. To summarise:

Radiator 1: Successfully bled (yeah!). Water came out at high pressure, some dark coloured but not an alarming amount and otherwise clear water. Note, after this I did not adjust the pressure valve (I think this is the relevant gauge….
It’s the only gauge in the house I can see - sits atop a bent braided pipe, next to a red cylinder about a foot high which I assume is a “sealed system expansion vessel” - I’m having some trouble identifying as I don’t have manual and comparing to diagrams online which are black and white. It is currently at 1.5 mark (with heating off, and hot water heater on for 1 hour early this morning). 

Radiator 2: Poked at with a sewing needle and a mug load of (clear coloured) water came out. Not at high pressure and not as much as radiator 1 but I’m hopeful this will make the difference. 

Note re: pressure - I’m not sure if the radiators pressure work independently or all together (hope you understand what I mean).

Radiators 3 and 4: screws are too damaged to turn at all. So I guess I need a wrench, and replacement screws (if they can be poked out) or replacement valves. I’m hopeful these can just be taken off with a wrench and replaced easily enough. 

Pressure gauge on the red tank throughout seems to be 1.5 (but that’s when the heating is off so presumably this will increase when water is heated). I’ll check. I will also check and see if the 2 radiators water now heat up properly (I.e the top of them gets hot as well as the bottom). 

 

Fingers crossed! 

[Deleted User]

Courteous said:

Radiators 3 and 4: screws are too damaged to turn at all. So I guess I need a wrench, and replacement screws (if they can be poked out) or replacement valves. I’m hopeful these can just be taken off with a wrench and replaced easily enough.

Hi,

are you using screwdriver or this,

Courteous

[Deleted User] said:

Courteous said:

Radiators 3 and 4: screws are too damaged to turn at all. So I guess I need a wrench, and replacement screws (if they can be poked out) or replacement valves. I’m hopeful these can just be taken off with a wrench and replaced easily enough.

Hi,

are you using screwdriver or this,

Hello,
Flat head screwdriver. I don’t mind buying one of those if that might work - just thought that as the screw heads are mangled it wouldn’t. 

Bendy_House

Courteous said:

Brilliant - thanks for the input. Feel a bit less stuck/closer to identifying the problem/s and solution. To summarise:

Radiator 1: Successfully bled (yeah!). Water came out at high pressure, some dark coloured but not an alarming amount and otherwise clear water. Note, after this I did not adjust the pressure valve (I think this is the relevant gauge….
It’s the only gauge in the house I can see - sits atop a bent braided pipe, next to a red cylinder about a foot high which I assume is a “sealed system expansion vessel” - I’m having some trouble identifying as I don’t have manual and comparing to diagrams online which are black and white. It is currently at 1.5 mark (with heating off, and hot water heater on for 1 hour early this morning). 

Radiator 2: Poked at with a sewing needle and a mug load of (clear coloured) water came out. Not at high pressure and not as much as radiator 1 but I’m hopeful this will make the difference. 

Note re: pressure - I’m not sure if the radiators pressure work independently or all together (hope you understand what I mean).

Radiators 3 and 4: screws are too damaged to turn at all. So I guess I need a wrench, and replacement screws (if they can be poked out) or replacement valves. I’m hopeful these can just be taken off with a wrench and replaced easily enough. 

Pressure gauge on the red tank throughout seems to be 1.5 (but that’s when the heating is off so presumably this will increase when water is heated). I’ll check. I will also check and see if the 2 radiators water now heat up properly (I.e the top of them gets hot as well as the bottom). 

 

Fingers crossed! 

Hi Court.

Yes, the proper 'bleed tool' as shown by Frug is best. If you'd like to post a close-up photo of the bleed screw, then it should hopefully be obvious to us what's amiss.

Yes, the red vessel is an external expansion vessel, so presumably means that the one that was inside your boiler is kaput. Or else perhaps your system is soooo large, that an extra EV was required. Doesn't the boiler itself have a pressure gauge? (Make and model of boiler, please?)

As you surmise, when a sealed system like yours heats up, the 'system' water expands and needs somewhere to go if it isn't going to cause the pressure to soar alarmingly. That place is the EV. A well set up system should remain at a fairly constant pressure whether hot or cold - perhaps edging up 0.2 bar or so when hot, before returning when cold. It's very tolerant, unless the pressure climbs at a fast rate, and goes over, say, 2bar.

As it appears, your system pressure is around 1.5bar. That's fine. Yes, as you bleed rads and release some of the water (and any rapped air), you'd expect the pressure to drop. This depends, tho', on how much water/air you release, and what your system volume is like to begin with (ie, a large system will have less effect).

Some Qs:

1) The rads you managed to successfully bleed - did AIR come out, or just water? If only water, then 'air' probably wasn't the issue in the first place.

2) After the initial slug of dirty water, was the rest quite clear? You seemed to think so, but this can only be judged properly if decanted into a clear glass and looked through.

3) Do you have a magnetic filter fitted to your system, on the return to your boiler?

4) Does everything else seemingly work ok?