Any unusual noises should always be treated seriously.One of the first things to check if a boiler is unusually noisy is the boiler's thermostat. If the thermostat is malfunctioning, water can become too hot and begin to boil, which could cause loud noises. If the thermostat is broken it may need to be replaced to prevent the water from heating up so much.Another reason for a noisy boiler could be mineral deposits. As the water heats up inside the boiler, minerals may sink to the bottom of the tank and affect the heat exchange. This may create hot spots within the boiler in which water is overheated, leading to loud noises. Low water pressure is also a concern that can result in loud noises. If water pressure is low, the boiler is tend to be overheat.