Musty Smell Radiator - Piglet John?

[HelenF35]

Hi, I know piglet John is usually a good source of information on here but any comments from others welcome. We've had a condensation issue in our bedroom which involved a mouldy built in wardrobe (against external wall). We've stripped the wardrobe wallpaper and treated and removed the mould. Near the cupboard there is a radiator under the window that had never been on. We turned it in and there is immediately a musty smell from it. It's been removed from the wall and the fins have been hoovered but it still smells. I'm convinced it's from the radiator itself (rather than the wall) as I can smell the smell if I sniff the radiator when it's cold. There is no visible mould behind the radiator or on the wall. Any ideas what might be causing it and how to treat? I thought it was just dust burning off for a start but it still smells days later.

[HelenF35]

Just to add there is some corrosion to the radiator but no leaks.

[PigletJohn]

look at the floor under the radiator. Any sign of water stains? Scrub the ends and bottom seam of the radiator. If it is corroded it is quite likely to be leaking. A hot radiator will evaporate away water drips before you see them. Look at the radiator pipes and feel them when cold. Clean off any scale or rust. They might also be leaking under the floor. Lift a board if you can, and sniff.

Turn off the radiator at both ends and open the bleed screw to verify there is no pressure in it. Does the smell reduce?

You could take the radiator off and wash it with WUL and a nylon hand-brush. Possibly there is some unpleasant substance on it. Or it might be the wall behind.

[HelenF35]

Definitely not leaking. No sign of water stains. Have checked it hot and cold by wrapping toilet roll around the inlet and outlet to double check. No pressure in the radiator and smell has lessened slightly since we checked but think that's more to do with the dust removal from the back of the radiator which was done at the same time. It's a mystery! Going to give it a good clean and see if that helps. Otherwise might just replace it. My partners father used to be a heating engineer and he says he's never seen this before. I suspect there is mould on the radiator somewhere, the smell starts immediately the radiator is switched on.