Radiator-TRV advice

[richmof]

Sorry if this question has been answered but I couldn't find the answer. Anyhoo, the TRV pin on my radiator keeps sticking. I can get it to pop out but, as soon as I put the TRV head back on, it just sticks...no matter how many times I try to pop it out manually.
Is it bust and in need of replacing? If so, is this straightforward?

Got another rad where the pipe leading to the TRV is cold, even when the pin is fully extended. Have tried all the usuals: bleeding, regulating the pressure in the system, taking off the TRV and tapping the pin out, the old reliable spanner taps...Any other ideas?
The problem - with the second radiator - began after my girlfriend drained the radiator (she was trying to bleed them and didn't ask me how to dos so). Do I have a big air bubble in the system and, if so, how to I clear it?

Sorry if these are stupid questions but they don't seem to be answered in the FAQs.

 

[John506]

For the stuck down pin, use WD40 and tap the side with a hammer, when it's popped up, squirt it again all over the pin to ensure it's well lubricated.

For the cold rad, to clear an air bubble you would usually just give the pipe a tap where you think the air bubble is when the system is on. The valve could be blocked with something.

I went on a job once to a radiator that wasn't heating up at all, and when I took the lockshield off, there was a big clump of gunge blocking it, looked like old paste.

How far from the boiler is the cold rad, your system may need balancing.

 

[richmof]

For the stuck down pin, use WD40 and tap the side with a hammer, when it's popped up, squirt it again all over the pin to ensure it's well lubricated.

How far from the boiler is the cold rad, your system may need balancing.

Will get out the WD40 (or the Belgian equivalent) tonight. Thanks for that. The cold rad could be one of the last rad's on the loop, so I will try balancing at the weekend (never done it before but there is a detailed explanation in the FAQs).

Thanks for the advice - have found it tough to find a good plumber in Brussels, so DIYnot has helped me no end.

 

[richmof]

For the stuck down pin, use WD40 and tap the side with a hammer, when it's popped up, squirt it again all over the pin to ensure it's well lubricated.

WD didn't work its magic. Looks like I need a new valve. I don't think I trust myself to install either.