Pottertonflow sure + internal leak

[peter p]

Hi
Newbie to the forum, with a desperate problem.
11 year old oil fired Flowsure+ combi boiler with on board storage. Have had constant problems with various leaks but have managed to find and fix them. The pressure has been dropping off over a week or so. Traced this to PRV (water seen coming out of vent pipe), so replaced it.
After that pressure was dropping overnight causing it to cut out (red light on front panel) by morning. I topped it up and it worked for about another 24 hours before cutting out again. I then noticed water sitting in the base of the boiler. It is now loosing pressure in a few hours but despite examining everything I can see with the top and front panels off and cannot see any witness marks or drips.
I dont want to write the boiler off but if I can trace this leak I may have too. Has anybody any ideas. Have also checked the pressure vessel, no sign of water coming out of the valve and the pressure seems OK at .5 bar.
Any help or pointers would be appreciated, thank you in advance

 

[Gasguru]

Perhaps it's the thermal store or the boiler heat exchanger.

 

[peter p]

Perhaps it's the thermal store or the boiler heat exchanger.

thanks for the reply Gasguru, I have thought that and tried to find pictures or diagrams that would give me an idea of their construction, water flow etc but cannot find anything. Being ex motor trade I can in most cases work out how to etc from such information, does the heating water pass in an out of the ex changer and then into the storage tank via an external pipe (a separate unit) or does it form part of the "on board" storage tank with seals or similar between the two, do you know?

 

[peter p]

This has me baffled-It was almost at zero pressure when I got home last night, refilled it to 1.5 bar at about 11pm and by 7am it was on zero again and the boiler base was total wet with a little standing water. Topped it up to1.5 bar before leaving for work and at 6.30 tonight still has 1.2 bar and is perfectly dry inside. I am out of ideas why.