Sime boiler heat exchanger question?

A leaking heat exchanger is very dangerous! It means that the metal has corroded to the point of failure. The leak will never get any better, it will only continue to grow worse. 3 bar of pressure is fairly substantial. 1 bar is the equivalent of 1 atmosphere or 14.7 pounds per square inch. 3 bar then is equal to nearly 45 psi. Every square inch of the heat exchanger then has nearly 45 pounds of pressure attempting to push its way through the metal. The water in the heat exchanger will be considerably hotter than 212 degrees F under 3 bars of pressure. If the metal fails the water will flash to steam, expanding in the process. That's like igniting dynamite. It can and will do major damage to your home. You need to have a qualified boiler service technician come in and check out the system. It is possible that you may need a new heat exchanger. It is also possible that a gasket is failing and needs to be replaced. Yet another possibility is that water vapor in the combustion gases is condensing as it gives up heat in the heat exchanger. Those problems each require a different fix. Be safe and call in a technician to determine the exact nature of your trouble.