Pressure dropping and pilot light cutting out

Ive been having a series of ongoing issues with my sime friendly format 80E boiler.

2 things are happening simultaneously. Firstly I have the pressure issue. Since i moved into the house (6 years ago) the pressure in the boiler has dropped ever so slightly and required a top up about every 3-4 months. I took this as a small leak under the floorboards downstairs, but it was so minor I paid no attention to it. Recently the pressure will drop to 0 within a week and if I have refilled the system to 1 bar it will shoot up to 2.5 bar when hot (seems a little too much).

Secondly the pilot light is randomly cutting out even though the pump will continue to run. If i turn off and turn on it will kick in again and the hw or ch will work as normal.

I recently had to change the diverter valve and have been reading that the pilot light issue might have something to do with the pcb, but has that got anything to do with this pressure issue ive now got?

Any help would be greatly appreciated as the plumber i called out a few days ago seemed to know less about boilers than i do from just reading this forum.

This forum has a lot of useful advice supplemented by some good boiler experts.

It sounds as if your expansion vessel is failed or needs recharging.

Look at the FAQ on this site or call a boiler engineer ( rather than a plumber! )

Tony

My guess is that you are looking at 3 different problems.
Small leak has become big leak.
Lack of maintenance has deteriorated the whole system including the boiler.
Pilot failure could have various causes

Cheers Tony, by plumber i meant boiler engineer (probably insulted a few people there) and we did discuss the vessel, however his description of a vessel failure is different to that on the faq (probably cos before i made it home he was trying to sell a new boiler to my wife). Looking at the faq closer it does make far more sense than what he was telling me. Would a drop in pressure cause the pilot to cut out? If so it might just be the that.

As ben mentioned it may have various causes but I have tried to have it reasonably well maintained since I moved so am hoping its just one part.