Radiator cold at the top only

[Poptician]

Hi

I've just fitted a new radiator after first draining the system and then refilling. The new rad is only getting hot at the bottom and not the top. I've bled every rad where possible (3 don't have a bleeder valve) and switched the pump on and off quickly to try and get rid of any air.

What concerns me more is that when I try to bleed the new rad (a double with fins as opposed to the single one I had before) neither air or water comes out. It does absolutely nothing.

Any ideas?

 

[breezer]

it may sound daft but have you turned the valves back on?

 

[Poptician]

it may sound daft but have you turned the valves back on?

Yes - the bottom of the rad is hot.

 

[breezer]

have you bled the pump? (as in radiator, but big screw in the middle)

 

[oilman]

did you turn the pump OFF before bleeding?

There MUST be some way of bleeding the rads, even if they appear to have no bleed valve.

 

[corgiman]

is this a new rad or a replacement.

Just wondering if you have put in a new one slight higher the the f and e tank say in the loft?????

just a guess

 

[MANDATE]

I think I would be tempted to turn off the valves again and remove the whole bleed valve assembly for examination to ensure there is a path through for the air and water.
I would also be tempted to crack open a valve slightly while the assembly is removed. All this of course with the system off.
If there is no sign of air followed by water then I would assume there is no head of water to create the slight pressure required.
Pipe work layout that forms a inverted 'U' can cause problems when re-filling, it fills from both sides and you can get an air lock that can not be bled off easily. Air is compressible and in this situation needs to be moved along to either a radiator where it can be bled or the overflow/expansion pipe where it can escape without bleeding.
In the past I have removed a radiator and replaced it with 6ft of clear plastic tubing suitably attached to a bit of 15mm pipe with fittings to suit the radiator valve .
With this I found there was no circulation of water, then I removed one end only and ran off 2/3 buckets of water complete with air (it could be seen in the tubing), then repeated it for the other end.
It was successful because there was no resistance to flow and got rid of the air lock.It does not have to be clear tubing, but it was good to see what was happening.
hope it helps

 

[Poptician]

Thanks for all this, especially MANDATE.

I took off the whole bleeder assembly to find the hole was blocked. A simple pin prick did the trick. I'd racked my brains over this for almost a week.

Right - off to watch telly in Med temperatures!