why is my radiator hot at the top cold at the bottom?

Answer 1

Like I've told many others that answer this question ( It seems to be a regular question) I've never found air in the bottom of a radiator, although I think some of the advisers may have that problem.

Your problem is circulation, this can be a number of possible reasons, If it's an old system then it may be sludge but usually that's more than one radiator affected. The pump may be slowing down, again this usually affects more than one radiator. If the radiator is a big one then the pipework supplying it may be undersized or a long run or partly blocked. More a problem with mini bore systems. The valves may be part closed or the thermostat valve (if it is fitted with one) may have a sticking pin (remove head and free ). Try balancing the system first and work on the theory The largest radiator wants a full flow of water (both valves fully open) a radiator half that size will only require half the flow so close the lock shield valve down by half. The smallest rad just crack the lock shield open a 1/2 turn and the other rads in proportion.

Answer 2

It needs bleeding, this only takes a few seconds but you will need a special key to turn the end of the radiator. When you have a key turn the valve at the top corner(on the side) of the radiator, it will start to hiss, wait until the hissing stops and then very quickly turn the valve shut again. Some dirty water might leak out once the hissing stops so hold an old towel or something under it. It is just a build up of air in the radiator.

Answer 3

Because the hot water from the engine enters the radiator at the top, then it is cooled all the way down before returning back into the engine via the bottom of your radiator.

I may have picked your question up wrong. It is normal for the radiator to be warmer at the top because as I said that is where the warmest water enters the radiator, however if you mean that the radiator is stone cold then you do have an air lock.

Sorry m8, unsure what radiators you meant, I thought you were on about cars, but still it is air in the system, easy job bleed air out via air bleed screw on top of radiator on either side, open screw a little using proper tool and old towel to catch water, when the air noise stops and the water comes out smoothly close the screw,job done, your rad should warm up completely.

Answer 4

Nothing to do with bleeding. It may need flushed out.

Why?

If the radiator is cold at the bottom and warm at the top and this problem persists, then there may be some sludge at the bottom of the radiator and it may need flushing out. For this, the radiator will need to be taken off the wall, flushed out with water and refitted. This can be done by yourself if you follow the correct instructions and have a basic understanding of how your heating system works but if you have not done it before or are unsure of the procedure, then you will need to call a plumber or engineer out.

If several of your radiators have this problem and it is not solved by flushing the radiator out then the problem may be more serious. This could be caused by a fault with the circulating pump, blocked pipes or radiators or a badly designed system. You will need to call a professional out to look at this problem further as it may require the whole system to be flushed through or repairs to be carried out.

Good Luck

Answer 5

you need to bleed your radiators, get a key from your local diy store, and losen the valve on the top right or left of the radiator to release the air, when water starts to come out close the valve. your radiators will now be hot top to bottom.

Answer 6

Bottom section is cold or all radiators are cold or luke-warm -
This means rust and sludge are obstructing the bottom part of the radiator.
Found this on Homeserve website -emergency tips in the help and advice section

Answer 7

your radiator needs bleeding you should find a drain at one end or at the back you need a brass key for this which you can get from any diy shop you then turn the key to let the air out do this till water comes out and you will find the rad is hot from top to bottom when doing it hold a towel underneath to catch drips

Answer 8

hot water rises so all radiators are hot at the top than they are at the bottom. Normally you cant tell, sounds like the radiator needs bleeding.

Answer 9

puzzling

when my radiators need bleeding they are hot at the bottom and cold at the top

Answer 10

It has air trapped in it and you need to 'bleed' it with the special key. You need to turn the key slowly and keep a cloth wrapped around it. The air will make a hissing sound as it is released, but you need to tighten the key again really quickly when all the air has come out, otherwise all the dirty liquid inside the radiator will splurt out (hence why you use a cloth).