How to get rid of damp smell from a internal wall?

[pavka007]

I need some help from the PH collective brain power.

I just replaced number of radiators around the house. However the sizes are a bit different from the original ones, so after the new radiator in the main bedroom was installed there was a difference of about 2 inches (the new radiator is "lower" than the old one on the top).
There was some old wallpaper that I had to remove and after that I painted the whole wall, so no difference of the finish.
Now there is a damp smell coming from the area above the radiator that I've removed the very old wallpaper.(2X 15 inches)
I am stunned and don't know how to resolve this.
The wall is Internal and there is not any source of water not even close.

What could be the issue here and how to get rid of this smell.
(Just to add the wall is brick)

Thanks

[Pheo]

You sure the new rad isn't leaking? That'd be a source of water right there!

[pavka007]

Pheo said:

You sure the new rad isn't leaking? That'd be a source of water right there!

100% sure otherwise my carpet should be soaking.

[DrDeAtH]

Zinsser cover stain will sort out the smell if it is coming from the wall.

Check the pipework under the floorboards if possible, just to make sure none of it is leaking.