Citroen XM Forum

I'm sure I have one of these citroen "Bungs" in a box of sphere plugs. I now understand how they work. The bung is threaded so the gas adapter can lock down onto the sphere, with no other means of compression.

The original filling plugs are shear bolts, so after the sphere is full, the bolt is tightened until it shears off, leaving just the plug.

I can't see any reason the bungs you have couldn't be re-used, they will need loosening and possibly a new O ring. A lathe and milling machine and you could make them for peanuts.

Dieselman wrote:The original filling plugs are shear bolts, so after the sphere is full, the bolt is tightened until it shears off, leaving just the plug.

?? No signs of shear on any on the OE plugs I have. All are smooth sides and top, with just a few lines from where the stilson I used remove them.


O-rings:
These 2.62mm Viton items produce a more positive nip-seal to the sphere surface than the OE and Valprex items:
https://www.polymax.co.uk/catalogsearch ... q=BS110V75.
Has been written up before.

White Exec wrote:

Dieselman wrote:The original filling plugs are shear bolts, so after the sphere is full, the bolt is tightened until it shears off, leaving just the plug.

?? No signs of shear on any on the OE plugs I have. All are smooth sides and top, with just a few lines from where the stilson I used remove them.

Look at enough bongs and you will see ones with the shear there, not properly ground off. It may be that newer ones have a different method of gripping the bung, but I doubt it because, as you have noted, it leaves marks.

Shear bolts are commonly used for single use bolts on cars, such as steering locks.

Here's a few more pictures of the valves as requested:







That's me recharged 4 of the 6 spheres on the CX now, the main accumulator, brake accumulator and both front spheres, there's no room to regass the rear spheres in situ and to get the sphere off you have to remove the whole strut so that was a job for another day.

David.