How much torque dare I apply to this lockshield?

[Radian]

I've bounced off of doing this job for too long now. A towel radiator tail needs re-doing as suggested by the crusty white deposit all around it:

But I can't get the lockshield to turn to isolate the radiator for draining. The amount of torque I'm applying with the adjustable seems like it's going to break something. In people's experience is this likely or do I just keep on leaning into it?

Also, could this weep be the source of the air I keep having to bleed out of the system? Is it really possible that this could let in air - there's never any sign of water or dampness - just the crust.

 

[Last Plumber]

Yes it will break as it is made of brass and that is weak enough without the time/corrosion factor.
Yes, in theory it can allow air in if it is leaking.

Can you not freeze the pipe or de-pressurize the system to allow the valve to be changed?

 

[Chuck]

A proper job would replace the seized lockshield. Would probably use a freezer, or partial drain-down, or bungs in the f/e tank if applicable.

 

[Radian]

Glad I asked then.

or partial drain-down

With my system even a partial drain-down is what I call the 'Nuclear' option as it takes a lot of effort to purge. But when I can next clear a day from my schedule that'll have to be the answer. I'm too chicken to use freezer.

 

[ShaunCorbs]

Can you undo the packing nut 1/2 a turn then try the valve