Help with Radiator Bleed Valve

[Caulsy]

Hi there I've not long moved into my property and the radiators have started playing up. It is a Gas central heating system and most of the rads are working. I was going to try and bleed the ones that where not working to see if this solved the problem but I can't find a bleed valve anywhere. Can anyone point me in the direction of them from the pics I've posted?

Thanks for your help.

 

[Last Plumber]

They're right there !
Two square ends !
Top of rad at the end.

Is this a sealed system or open vented ?

 

[Caulsy]

im not sure what it is sorry.

I thought it might be those square things but didn't want to touch them in case I messed it up.

Thanks very much for your reply it's greatly appreciated

 

[Last Plumber]

You might be better getting someone to help you.
If it's sealed it won't refill itself and you could end up with no heat and hot water.
If you are unsure, get a plumber/ heating eng.

 

[Caulsy]

Brilliant mate thank you

 

[Last Plumber]

No worries !