Alpha cb 24 boiler pressure over 2.4 bar, need help

[delboy1209]

I have a Alpha cb24 boiler, that has been leaking water out of the over flow pipe.
The boiler pressure gauge is over 2.5 bars when hot, when cold drops to a 0.5 bars,
I top up the pressure gauge to 1.5 bar, this happens 2 or 3 times a day, even if the central heating is not on. I Have replaced the pressure relief valve, After read some forums, but I still having same problem. Can someone help please.

 

[corgiman]

do a search on expansion vessels and how to re charge them