I have one radiator in my house that has gradually stopped heating up. It is now completely cold. Help?

Question

I have bleed the radiator and every other one in the house (there was no air in any of them). I have checked both valves (the thermostatic valve is not sticking). There is another radiator on the other side of the wall that works perfectly. I have a combi boiler and the pressure is about 1.5 bar when cold and 1.8 bar when hot. It stopped heating up about 2 weeks ago and as I said was gradually getting cooler over about a 2 week period. I could feel the intal pipe was hot but the is now not hot any more. I was wondering whether there is pressure from the outlet pipe stopping the water from flowing through...

Answer 1

There are some interesting suggestions in this article, which I'm leaving pretty much intact:

Cool top, warm lower:
As you feel the radiator, it gets gradually colder from bottom to top. This is an indication that there is trapped air, and it will be necessary to bleed the radiator.

! Bleeding a sealed central heating system reduces the pressure, so it will need correction. This is usually done by turning on the cold water feed. If you are unsure about re-pressurising, contact a plumber of heating engineer.

Bleeding - Make sure the heating is off and the radiator cool, then use the radiator bleed key to open the air vent on one side at the top of the radiator. Insert it and give it a ½ turn anti-clockwise: do not open it fully. Hold a cloth to the vent to collect any dribbles of water. The vent will hiss first as the air escapes. Once the water starts, close the vent back its ½ turn. Do not turn it too tight.

If you have bled your sealed system, check the pressure and top it up if necessary to 1 bar, or as the instructions state.

One or all radiators requiring frequent bleeding:
Problem radiators mean that air is entering the system somewhere. This could be caused by or is causing corrosion and may need a heating engineer's attention. It may be that black iron oxide sludge has built up in the bottom of a radiator and preventing the water's movement. To resolve this, add a sludge removal liquid to the feed/expansion header tank, then drain and refill the system a couple of days later.

If this does not solve the problem, it could be caused by leaks, faulty design, or lack of water. Serious problems will not be affected by radiator bleeding. Try examining the pump and the flow regulator:
Note the setting of the flow regulator, and then turn it on and off rapidly several times using a screwdriver. If that fails...
Bleed the pump via the bleed valve on the casing. Open and close rapidly. Any hissing means you have found the fault.
Downstairs cool, upstairs warm:
Colder lower radiators are a problem that can usually be traced to the pump. Start by turning of the central heating and allow time for the pump to cool. The pump is located in or near the boiler; it whirrs and vibrates as the motor works to push water through the impellers. If you need to manually start the pump, unscrew the centre and turn the impeller.

Another trick to try is gently tapping the pump a few times with a mallet, or it can be removed and flushed though with a hosepipe of clean water. If it still not working a new pump will be required.

Upstairs cool, downstairs warm:
Check that the feed/expansion tank is not empty. If it is, refill it with enough water so that the ball just floats. The water will expand when heated so allow extra space for this. Don't forget to check the ballcock and valve for leaks or corrosion.

Upstairs cool, except when programme is on hot water only:
In a gravity-based heating system the gravity check valve can switch off the heating, meaning that hot water from the cylinder will not reach the upstairs radiators. When the heating is on, hot water rises above cooler water. The gravity check valve is attached to the flow pipe toward the upstairs radiators. If it stuck open, the pipe running through it will be warm. This will require the attention of a heating engineer.

Of course, do not forget to eliminate the obvious causes first: are the thermostatic valves stuck low, or are the caps for the thermostatic valve bearing no relation to altering the temperature? You may need replacement thermostats.

Cool radiators furthest from boiler:
If the radiators get cooler at a greater distance from the boiler, this indicates that your central heating system is not properly balanced. This occurs on feed and return systems whereby the pipe flowing to every radiator is from the main flow pipe. At the furthest radiator, the main flow pipe turns back toward the boiler and becomes the return pipe, into which pipes from every radiator feed. The water does not flow in and out of each radiator in turn, but comes from the main pipe that feeds them all, and goes into the main pipe returning from them all. If the system is not balanced, you will not get the right feed to the furthest radiator.

When the radiators are first installed they are given a lockshield valve which allows for balancing adjustment. Once installed and balanced, they should not require further altering unless there are changes to the radiators or the pipework.

Balancing - Before you begin, turn off the central heating and give it plenty of time to cool down.

Locate the lockshield valve at one end of the radiator under a push on cover. Using an adjustable spanner, open the lockshield and the control valve (at the other end of the radiator) on all the radiators.
Attach radiator thermometers to the inlet and outlet pipes of the radiator nearest to the boiler, not to the main flow and return pipes.
Now switch on the central heating system.

Partially close the lockshield valve on the nearest radiator. As the temperature rises, slowly open the valve until the temperature difference between the two thermometers is about 20°F (12°F).
Attach the thermometers to the next radiator along from the boiler. Repeat the process as above.
Continue along all the radiators until they have been balanced.
The effectiveness of balancing the radiators can be affected by external temperature. If the external temperature is higher than the system design value, the heat disseminated by each radiator will be less than the design intends. Consequently, the temperature drop across each radiator will be less than 20°F. If the balancing occurs on a summer's day, adjust the lockshield valves to get a lower temperature difference.

Answer 2

Simple first turn off the heating and close both valves, open and remove the air vent, with the aid of a friend hold a bucket at the air vent and then open one of the valves, observe the flow rate out of the vent close valve and open other valve is the flow rate the same ? If so then the pipes are clear. Close valve , replace vent screw and open both valves.If the system had an air lock in the pipes then it most likely will have cleared and the rad should work.
If the flow rates were not as near as equal then you will know which pipe to further investigate.
You say the thermostat valve is not stuck, the pin may be free but the washer may be stuck inside the valve.
Next look at the manifold connections, If the manifold is the nut and olive type be warned the brazed connections snap off very easy.

Answer 3

Older radiators use steam not water to heat. It is a problem with the pipe leading to that one radiator that is the problem. Usually, the pipe will corrode and clog not letting any steam through to the radiator. Another problem that I have experienced with old steam heat systems is that a portion of the pipe can fill with water and freeze which usually happens in older systems where the boiler is old and cannot put out enough steam anymore. Because you never know where the frozen part is, the only way to fix it is to replace the whole pipe leading to that radiator or to replace the whole system with more modern heat.

Answer 4

I have the same problem in my daughter's bedroom. My husband did everything you just mentioned. He removed the floorboard between the two radiators and found a cracked and rusted pipe. Replaced them both and now she has the hottest room. He will eventually replace all the pipes, our home is over 80 years old. We also had the Public Service guy out to run a "free" maintenence check. They can usually tell you where the problem is coming from.

Answer 5

Try 'balancing ' the system by throttling down the other radiators a little to improve the flow to this rad. You may find there will be some air in the system but at the moment the pump cannot overcome it.

Answer 6

Sounds to me like there is a blockage. Unfortunately you need to drain the whole system and flush it out. Then refil with something special liquid to clear any rubbish out. Check all valves and start up again.

Answer 7

one of the previous answers is brilliant very comprehensive.I had one of my radiators do this a couple of weeks ago.All I did was to close up a couple of the other radiators and it seemed to make the cold radiator hot again.I then opened up the closed off radiators and it worked fine and has done since,may be worth a try?

Answer 8

It could be air bound that would indicate that you did not bleed it enough dont try it again just call an HVAC tech and have them figure it out for you you may be entitled to a free annual service and that would be the time to tell them of your problem.

Answer 9

try bleeding all the radiators when they are off if you have tried this sorry no other answer except call a plumber

Answer 10

HAVE YOU TRIED TO BLEED IT? This involves a rad key release the nob on the rad until hot starts to come out of the hole be careful water is really dirty though hope that helps