how can i fix my Worcester oil heatslave 15/19 boiler ?

Hi, my oil boiler keeps locking out. When you push lock out reset button it will fire up for between 5-10 mins on hot water or heating and lock out again. The system pressure gauge is over 3 bar which i know is too high ( normaly 1 bar ) & there's a small bent copper pipe outside next to flue that drips hot water. Is any of this the cause for lock out & how can i fix it ? thanks for any help, regards Paul.
This has happened to me before, long time ago now but i cant remmember how i fixed it.