Thought I would ask if anyone has any ideas.

My Boiler is a Baxi (Don't groan too much...) and started playing up a month or so ago. It kept losing pressure. So you assume there is a leak somewhere? Checked all radiators all ok.

So drained down the boiler completely. Filled it up, checked no air leaks in it. Filled it to 2 bar. Now it pressurises too much! Always at 3bar+.

Checked pressure in the expansion tank. Set at 1 bar as it is meant to be.

Sometimes the water is perfect, othertimes it is hot for 10 secs then stone cold. Changed the sensor on the hot water pipe too. Heat exchanger was replaced 6 months ago.

Any advice would be good!

My mate has a Baxi, it's blow off valve was leaking...have a check round that :)

Thanks mate. Blow off valve - The water pressure or?

Not too good on boilers....

Thought I would ask if anyone has any ideas.

My Boiler is a Baxi (Don't groan too much...) and started playing up a month or so ago. It kept losing pressure. So you assume there is a leak somewhere? Checked all radiators all ok.

So drained down the boiler completely. Filled it up, checked no air leaks in it. Filled it to 2 bar. Now it pressurises too much! Always at 3bar+.

Checked pressure in the expansion tank. Set at 1 bar as it is meant to be.

Sometimes the water is perfect, othertimes it is hot for 10 secs then stone cold. Changed the sensor on the hot water pipe too. Heat exchanger was replaced 6 months ago.

Any advice would be good!

When you topped up the system are you sure that you turned the valves back off compleately, if not this could be why the pressure is rising.
When you say you checked the pressure in the expansion tank, do you mean the water pressure via the gauge on the boiler or the air pressure via a tyre gauge.
Also remember the system pressure should be idealy 1-1.5 bar as when the water is heated this can rise up another 1 bar dependant on the size of the system and this is then getting close to the relief valve letting go at 3-3.5 bar.
Lastly if there is no air pressure in the expansion vessel or the diaphragm is split then no expansion can take place in the system and when the water is heated the pressure will go straight upto 3+bar and dump outside, then you will be left with a low pressure situation.

Hope that helps abit
Mog