Leaking Combi Boiler

[fredsshed]

I have a Worcester 18/25 external oil fired combi which was only fitted 2 months ago. The pressure drops after just a few hours so suspecting a leak I called back the fitter. He says there must be a pipe leaking somewhere under the floor but as he didn't fit the pipes he's going to charge a small fortune to find the leak as it involves removing and refitting lots of floorboards, carpets and tiled floors etc etc. This week i've exposed all the pipework and can't find any leaks whatsoever. I was told it could be a faulty expansion vessel and to but a poly bag over it, repressurize and leave overnight but the next morning nothing in the bag and no pressure again. Today I have tried closing both the flow and return valves in the boiler and then repressurizing the boiler. After just a couple of hours the pressure is dropping. There has never been any water under or inside the boiler so I am guessing the boiler is leaking internally. We have noticed that we get a lot of steam vapor from the flue but just though it was due to the very cold weather.
My question is, could the boiler be leaking internally into the combustion chamber and the water coming out as steam through the flue or could there be another reason. I just don't want to call out Worcester when there could be some other simple explanation.
Any help would be appreciated

 

[dcawkwell]

Yes your plumber is hopeless easy enough to remove the burner and look

 

[fredsshed]

I have opened the combustion chamber door and it looks very rusty inside, one side is black and sooty and the other very rusty indeed, can't see any water though. Where is the most likely place to find the leak? Would I presume right that the combustion chamber has a sort of water jacket around it? When you look inside the combustion chamber there is one patch of realy bad rust near a welded joint. Could the leak be in the combustion chabmer and not the heat exchanger?

 

[dcawkwell]

I have opened the combustion chamber door and it looks very rusty inside, one side is black and sooty and the other very rusty indeed, can't see any water though. Where is the most likely place to find the leak? Would I presume right that the combustion chamber has a sort of water jacket around it? When you look inside the combustion chamber there is one patch of realy bad rust near a welded joint. Could the leak be in the combustion chabmer and not the heat exchanger?

Burner at the bottom of the boiler remove that you will able to look in i would also remove the baffles if there is a leak the water is going somewhere

 

[fredsshed]

The burner is at the top of the boiler, underneath there is a large steel box with a bolt on door at the front (combustion chamber?) I have taken the door off and inside it is very rusty and there looks to be runs down one side. I've pressurized the boiler with the door off but no sign of water entering the combustion chamber.

 

[dcawkwell]

The burner is at the top of the boiler, underneath there is a large steel box with a bolt on door at the front (combustion chamber?) I have taken the door off and inside it is very rusty and there looks to be runs down one side. I've pressurized the boiler with the door off but no sign of water entering the combustion chamber.

try taking pressure up to pressure up to 2

bar boiler 2 monthold should be spotless notuh rusty