Radiator refusing to co-operate

[chad5k1]

Hi Folks
Strange problem. Everything working fine three weeks ago, not so now.

One radiator is not getting any heat, it is downstairs and I suspect one of the last in the loop.
I've check the TRV pin and it moves up and down fine.
I've tried to bleed it and there appears to be no air in it.
I've opened the lockshield all the way.
I thought perhaps I could turn the heating up to the max on the thermostat and then turn off the other rad's at the trv (all drayton, look older than version 4) to see if that forced heat to the problem rad. All that did was get the top of the rad warm, but the bottom is still cold.
Then I noticed that most of the other rad's were still hot - so all the trv's are shot. Had a fiddle with some of them and got them working again, some are more stuck than others and so I've left them for now.
Having done that, I ran the same test again and this time the problem rad got hot.
Turned all the TRV's back to the appropriate settings and the problem rad is stone cold again.

I though perhaps sludge, but;

Worcester Bosch 30CDi installed three years ago.
Power flushed system before install.
Magnaclean installed serviced annually with the boiler (last time was fairly clean and it was a week before the problem began)
Inhibitor is used.
Water softener is used and has been in place for many years.

I will probably be replacing the trv's that are broken (may as well do them all I guess), I'm not sure what the problem is with this rad, as I don't think that will help.

Been in the house for almost a year (25 year old house) and it was working fine until recently.
Thoughts?

 

[chad5k1]

The problem has progressed, I've found that one lockshield (is leaking and the boiler has dropped pressure as a result, I've now shut that, but it reinforces my belief that all the TRV's and lockshields need replacing). In a addition, now the rad in the room directly above the room with the non working rad has started to become very slow to heat up.
I've contacted 5 plumbers about this issues with the following details.
So far, not one has actually come back with a quote. Am I doing something wrong?

Every TRV (Drayton) in my property to my untrained eye appear faulty. Even when turned off, the radiators are burning hot. I have 15 or so.
I've also found at least one rad with a leaking lockshield. In addition, I have one radiator that is refusing to get more than warm (even then only at the top) and is mostly cold.
The TRV pin is moving up and down freely, I've opened the lockshield all the way.
The system is unvented, had a power flush before installing a new boiler and magnaclean three years ago, both recently serviced.
I'm presuming it needs draining down, each TRV and lockshield changing, one rad checking for sludge and cleaning if required and then re filling with inhibitor adding back and balancing.
Can you provide a quote?

 

[muggles]

Looks quite sensible to me. Where in the country are you? Someone on here might be able to help

 

[chad5k1]

Maidenhead, Berkshire

 

[mazperks]

If the problem rad is getting hot with others turned off, your main problem is balancing.
Following new boiler powerflush and magnaclean, system should be fairly clean.
For the moment turn down all upstairs lockshields to half a turn open and see how it goes.
Similarly with rads closest the boiler downstairs adjust down if neccessary.

 

[muggles]

@Mike_W anywhere near you?

 

[Mike_W]

I am in Bracknell,so not too far away.

 

[muggles]

@mazperks Mike is a good chap, have a PM conversation with him and I'm sure he'll sort you out

 

[chad5k1]

FYI, as an update.
The 2 radiators not getting hot was solved by increasing the boiler pressure. It had dropped to less than 1, into the red. I topped up, just a little bit to just over 1. I suspect the service caused an airlock or something and this drop in pressure was exacerbated by the lock shield leak on one of the rad's.
So still looking to get all TRV's and Lock Shields replaced.