beeding radiator, new sealed system

[gxr]

Had an old central heating system with lots of problems (e.g. bathroom radiator needed regular bleeding). Just had it updated 1) to a sealed system 2)new Ariston boiler 3)all radiators replaced 4)new hot water tank i.e. all thats left of the old system is the pipework beneath the floors.
After 1 month, the bathroom radiator is now cold at the top again.
Is this normal (perhaps some air trapped when the system was commissioned?)?
If there was a leak in the old pipework, what would happen?..Because its at pressure, I guess water would leak out but how does air get in if the system is sealed? I havent noticed a drop in the 1 bar pressure..would it drop significantly if theres a leak?
Thanks for any advice.

 

[croydoncorgi]

Check that the rad is really filled with air. Might be hydrogen! See other thread mentioning this problem and be careful not to light the curtains!

 

[IanDB]

Is this normal

Yes, try bleeding the radiator to get rid of the accumulated air. It will settle down after a while.

would it drop significantly if theres a leak

Yes, it would go down to zero after a while depending on the rate of leakage. After bleeding the radiator you'll probably have to top the pressure back up to 1 bar again (it's the same as having a leak.)