Reasons Why the Radiator is Not Heating Up

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Is the radiator not heating up? This is one of the most common problems you’ll encounter throughout the life of the heating appliance. But what’s causing it? Here are some reasons:

There are air pockets inside

Is the radiator cold at the top and fairly hot at the bottom? That usually indicates that there is an air pocket in the system. Air is taking the space that’s supposed to be for the hot water. This prevents proper circulation in the radiator.

Malfunctioning thermostat

If you notice the radiator not heating up, one of the first things you should check is the thermostat. There could be an issue with the thermostatic radiator control valve. It could have switched from being set on a particular temperature to being completely switched off. This usually happens when it’s set to a higher temperature because it’s fairly common for radiator valves to seize up in a closed state.


Is your radiator cold at the bottom and hot on top? The problem could be caused by blockage, which can be sludge or debris that has accumulated over time. The radiator won’t heat up because the blockage prevents hot water from circulating. The best way to fix this is by calling a professional heating engineer.


A leak doesn’t necessarily mean that you have to replace your radiator. It may simply signify corrosion because of lack of maintenance and cleaning. If it comes from the area where the thermostatic radiator valve is connected to the radiator or pipe, check if there’s a loose nut that needs to be tightened.

Knowing the exact reason why the radiator is not heating up can help you diagnose the problem and fix it properly. To eliminate the guesswork, consult with a professional and Gas Safe Registered heating engineer.