Signs That a Boiler Should be Replaced
Many of the signs that a boiler needs to be replaced can be seen with a simple visual inspection. Look for sufficiently worn down parts on the sheet metal on the outside, as well as on any visible piping. Also check for eroded electrical parts. Any wires, and sometimes electrical panels, will show signs of wear. A lot of rust on the boiler itself is another sign that it may need replaced. Make sure to check for leaks where you can. Pipes are common for leaks, but be advised that some may not be easy to find. Pipes that run in places that can't be easily accessed may be leaking. Parts insides the boiler itself, such as the heat exchange, may also leak, without showing any outside evidence.
Other Things to Consider
If a boiler is not too old, it may also have been installed improperly. If pipes are banging then just the pipes would need to be replaced, but if the boiler is not large enough for what it is suppose to do, because of a mistake from the past, then it will need to be replaced.
Lastly, if you're still unsure about replacing a boiler, some home inspectors will check boilers for defects. Going this route, it is important to research a particular home inspector before hiring, as they all offer a variety of different services.