Bleeding should not directly cause the boiler to stop working. However, if excessive bleeding leads to low pressure in the
Keep in mind that you shouldn't get carried away and open your radiator valve entirely or keep it open for too long - too much water will pour out, and your boiler pressure will drop dramatically.
If you let too much water out of a radiator, the overall pressure in your central heating system can drop. This may result in the boiler shutting down or the heating system malfunctioning.
Air pockets, inadequate water pressure and faulty radiator valves or TRVs are the three primary reasons why radiators do not work after bleeding.
We want to make sure that no water comes out. Occasionally you'll get a bit of water come out as the pressure dissipates from the radiator, but it should stop quickly.
It can take anywhere from 20 minutes to over an hour to completely drain a central heating system. This completely depends on your system, whether or not you have a drain-off valve and if you run into any issues during the process. Remember to open the bleed valves on all of your radiators to help speed up the process.
You should hear a hissing sound as the trapped air begins to escape. As the hissing sound stops and water starts to trickle out of the bleed valve, it indicates that the trapped air has been released. Once a steady stream of water appears, close the bleed valve by turning the radiator key clockwise.
If no water or air comes out when you bleed the radiator, then the valve could be blocked with paint. Close the inlet and outlet valve at each end of the radiator, then remove the screw from the centre of the bleed valve.
If your radiator is hot at the top but cold at the bottom, there may be a build-up of scale, rust, or sludge which is obstructing the flow of water. As with the middle of the radiator, if you have an open-vent system which is unpressurised and tank fed, you'll be able to use a sludge remover to flush your radiator.
Loose or damaged radiator spindle
The radiator spindle, which is the joint that connects the valve to the main radiator unit, can often cause a leak. Most of the time it's because the spine has come loose and simply needs tightening, but it also may be damaged and need replacing.
Aside from the danger of working with a radiator that has the heating on, it's also an inefficient bleeding process. If the pump is running when you let out air, this will actually cause the system to draw in more air from elsewhere.
Simply draining the radiator may get rid of most of the old antifreeze but could leave some coolant and contaminants behind, which would then mix with and pollute your new antifreeze and cause overheating. You want a full flush, a forced removal of anything old so you can pave the way for new fluid.
What happens if you bleed a radiator for too long? Bleeding the central heating system for an extended period isn't recommended as it can lead to pressure loss in the system. This can result in potential damage to the boiler.
If you overfill your car's cooling system, the excess coolant could cause electrical damage to the vehicle. Therefore, you should pay close attention whilst filling to avoid going over the maximum fill level.
Can you bleed a radiator when the heating is on? No! It's very important to make sure your heating is off, and the radiators are cool before you bleed them. This is because radiators are filled with water and air, which is what escapes when you open the valve (include link to new pressure release guide page).
Yes, it is perfectly normal for water to escape when a radiator is bled. You'll likely notice some drips emerging when initially turning the bleed screw in an anti-clockwise direction. And water would pour out once the air was released, if the valve was to be opened fully.
If you have recently bled your radiators, the pressure will drop slightly because you've released the trapped air in the system.
Don't worry if some black water comes out when bleeding the radiator. It's normal for it to be discoloured, as sediment can settle around the valve.
On the side of the reservoir, it has an L(low) and F(full) markings, and as the tank is translucent, you can see your coolant level without opening the cap. If the fluid is close to or below the L marking then you need to add more coolant to the reservoir.
How long does it take to bleed air out of the cooling system? Usually, it takes about 15-30 minutes, depending on the model and method you follow. It, however, takes 15-20 minutes to heat the engine and get rid of the coolant.
Open the bleed valve to release air
You should hear a hissing sound as the trapped air begins to escape. Be prepared for water to come out as well, so keep your container or old towel close to hand. Slowly keep turning the valve anticlockwise until the hissing stops and water flows steadily.
If the coolant level is dropping and there is no external leak evident, then the coolant is probably leaking internally, into the engine. If the car has recently overheated then this could have caused the head gasket to fail.
The coolant reservoir will have a 'Full' line indicator. Add water until it reaches that line. When adding water directly to the radiator, fill it to the brim.