Hi fellow brick lovers.
the top bolt securing the radiator was well stuck and trying to undo it the captive nut on the frame decided to be free !!! so after much cursing and broken drill bits the rad was also free.

Question: bolt length and thread maybe M6 or M5, so I can have the captive nut replaced (unfortunately in the surgery required to remove the captive nut and bolt nothing survived  )

M6x40

Many thanks Mr Duck

Number 10 if you have a K100 ;

https://www.realoem.com/bmw/en/showparts?id=0521-EUR-08-1988-K589-BMW-K_100_88_0521_&diagId=17_0625

long way from home wrote:Hi fellow brick lovers.
the top bolt securing the radiator was well stuck and trying to undo it the captive nut on the frame decided to be free !!! so after much cursing and broken drill bits the rad was also free.

Question: bolt length and thread maybe M6 or M5, so I can have the captive nut replaced (unfortunately in the surgery required to remove the captive nut and bolt nothing survived  )

its just a standard 6mm captive nut often found in electronic rack systems for mounting hardware 

several are used on the frame mounts 

you will find some at your local it professionals spares boxes 

stainless versions might last longer 

good luck

I haven't done any radiator installs lately but it MIGHT be possible to do it without a nut actually welded on there.

Difficult to get to the nutty end of the bolt, hence the captive nut.

Probably go with a weld in cage m6 nut, zip zip with a MIG welder and it's done. Now who as a MIG welder near me?