A common problem that occurs in a radiator is that when you turn it on, it gets hot but suddenly goes cold, or it wouldn’t even heat up from the beginning.

The first remedy that every owner will try is to bleed the radiator from the trapped air that’s inside of it. If this doesn’t work, then there must be other issues that the radiator has.

Here are several reasons which can lead to a radiator to go cold.

Stuck Pin on Thermostatic Radiator Valve

Having a stuck pin in the thermostatic radiator valve (TRV) means that water can’t flow into the radiator, which prevents heat from circulating the system. This can be checked by taking off the cap of the TRV and check if the exposed pin is stuck in a shut position. 

To solve the problem, the pin needs to be loosened up with a spanner or a grip. Turn on the radiator and check if it gets hot once the pin is able to move freely.

Air Lock in Radiator

An airlock occurs when vapor gets trapped in the heating system and stops the circulation of water in the radiator. You can fix this by removing any radiator cover you have in place and flush the air out of the radiator.

This can be done personally or with a plumber as it requires plumbing skills to take care of an airlock. Aside from that, you also need to bleed and disassemble the radiator.

The entire piping system is then cleaned out by removing the water inside it and being replaced by a new one.

Unbalanced Heating System

Another reason why the radiator is cold is that the flow of water in the heating system isn’t balanced. The uneven distribution of water in the heating system means that it can’t reach the radiator and makes it unable to produce heat.

To balance the heating system, other radiators in the house need to be turned off while some are turned on. This lets the heat to circulate properly and heat up the specific radiator.

Thermostatic Radiator Valve Needs Replacing

The TRV can degrade over time, especially when the radiator is frequently used. A reason for this is that the pin valve may have started to degrade or have become too difficult to move.

Having a new TRV can even improve the performance of the radiator and make it feel like it’s brand new due to its performance.

Incorrect Water Pressure

If a radiator has incorrect water pressure, then it might be the reason why it’s not working properly. 

There’s an indicator called a “Manometer” in the radiator to see if this is true. The regular water pressure will depend on the type of radiator, but most of them have a standard of 12 PSI when cold.

If the water pressure is too high, then releasing the pressure valve can help balance it out. But if the pressure is too low, then the solution is to add more water.


Regular maintenance is essential for a radiator to function properly. The efficiency of a radiator also depends on its condition, so it’s best to keep it in good condition as much as possible.

It might cost you some bucks, but it’s worth it knowing the many benefits you can gain from it.