When you can’t bleed a radiator?

A customer had a radiator that he couldn’t bleed but also wouldn’t heat up past halfway. He knew how to bleed a radiator but no air would come out.

He had already figured out the price for replacing his broken radiator when I arrived.

Luckily for him, I’ve seen this many times and it’s easy to diagnose where the fault is.

How to bleed a radiator

To bleed a radiator you use a small (normally brass) key that fits the square bleed point. The key is turned anti-clockwise which opens the bleed point and lets the air out. When the air is gone, water will start to come out of the bleed point. Turn the bleed key clockwise to reseal the bleed point.

Why won’t my radiator bleed?

When you bleed a radiator the air has to come out of an opening inside the bleed point. On this particular type of bleed point (myson radiators) the opening is very small. As it’s so small it very easily gets blocked up by sludge or dirt in the system.

Even when the bleed pin was completely removed there was still no air or water coming out.

Proving the hole is blocked

However, when I turned the whole bleed point fitting air (followed by water) did come out. Proving that there was no fault with the radiator itself.

Unblocking the hole

The simple solution to this problem is to poke a fine needle into the hole. This breaks the dirt crust and allows the water and air to come out. First, you must turn off the valves to the radiator and put a tray and some towels under to catch any spilled water.

You have to remember that sometimes the valves will not turn off the radiator especially if they are old. So if you are not competent or confident please get a professional in to do this job for you. If the valves do not close properly the water will come out very fast and can be very dirty.

As soon as you break the dirt the air will come out (quite fast). The idea is to get the screw back into the fitting as fast as you can (without cross-threading it) so no water is spilled. The time you have to do this depends on how much air is in the radiator and how much pressure is in the system.

The drip tray and towels are your very best friend if you can’t work quick enough.

Replace the faulty bleed point

The permanent fix to this problem is to buy a replacement bleed point. They are widely available although replacements tend to be chrome rather than white.

Close the valves and release the pressure in the radiator. Unscrew the bleed point and catch any spilled water with a towel.

Unscrew the bleed point and replace it with the new shiny version you’ve just bought.

Summary

The most common problem with radiators is air trapped inside. Although bleeding the radiator is a simple solution, it may not always work. This guide explains one frequent cause of unsuccessful radiator bleeding.