Radiator bleed screw

[hogie]

whilst bleeding my radiator i have managed to over tighten the bleed screw and snap the square end off the rest of the screw. to try and remove the rest of the bleed screw i have used a drill and some screw extractors but have been unsucessful in doing so. the type of radiator in question is an old type round topped radiator which does not have the facility to use a spanner to bleed the radiator. what i am wondering is if anybody has come across this problem before and what have you done to resolve it?

[Bob Minchin]

We had this one recently and my idea was to abandon the broken one and just fit a new bleed screw in the other end of the radiator.

Bob

[hogie]

Hi Bob,

Thanks for getting back to me, what size did you drill and tap the hole for the new bleed screw?

Thanks.

[Bob Minchin]

Hi Hogie,

No drilling and tapping needed just take out the blanking plug and fit a complete bleed screw assembly. Thread is usually 1/2" BSP but there are other sizes here

you will need a little ptfe tape to seal it too.

hth

Bob

[hogie]

Thanks bob, but the radiator that i have is one of the really old style ones there is no blanking plug on the other end, its a sealed radiator

Hogie

[Roger Mills]

Does it have a flat welded-in plate at the opposite end, or is it just rounded over?

If it's a flat surface, you may be able to drill and tap it and fit a bleed assembly. The smallest one listed in

[No: 91015 - 1/8" BSP] would be the best. You can't just drill and tap for the centre pin because it would have no seat to seal against.

If there isn't a flat surface at the end, you could drill and tap the back face of the radiator, just down from the top. It's a bit awkward bleeding it in that position - but not impossible. Indeed, some modern radiators have the bleed screw factory fitted on the back!

[hogie]

in

91015 - 1/8"

thanks roger,

but the radiator that i have has no flat surface on the end of it, the bleed screw that i damaged is at the back of the radiator, what size tap do you think would be best? and how far in do i go?

[Roger Mills]

If you use the fitting which I suggested (above) you'll need a 1/8"BSP tap. A 1/8"BSP thread is 0.383" (9.7mm) in diameter and has 28 threads/inch. The fitting won't actually look like the generic picture on the Toolstation website - but will have a shoulder outboard of the thread. You'll need to drill and tap right through the wall of the radiator, and screw the fitting in so that the shoulder seals against a fibre washer.

[You'll get a better picture of the little fitting on the BES site. Go to and type "Air vent" (without the quotes) into the product search box. Select the first offering (Diverter valves and air vents) and scroll down to Air Vents. The small one (6916) is what yours will look like.]