red flashing light, steaming and gurgling

Help!!
My boiler has filled the entire cupboard with steam, the top box (which is full to the 'maximum' level) is bubbling and boiling constantly and making really loud gurgling, bubbling noises!!
I looked through the manual, and found the display inside the boiler. It is currently showing the 'on peak supply present light' only and the 'locked out' light is flashing. I tried a reset, but it only worked for a couple of seconds before going back as before.
I have turned it off for the night to cool down, will I need to try to get an engineer out? (this is a problem because my landlords are useless and it'll probably take a week) or can i fix this myself through i series of button presses??
thanks for any help!!

ok, after a little more manual reading and pressing buttons,
it tells me: E3 51

so.. its over heated... and a sensor has shorted?
can i fix this?

Hi,

Usually with an E3 code mean that the sensor has failed as it is reading over 99 degrees, this will need repalcing.

Kind regards

Gary
MK Group Ltd

ok, i'll start pestering my landlords then.
thanks!