I just need some guidance in how to read the "Self Tap screw" size used to tighten the Exhaust solenoid on my Citroen. I have lost the screw.

The Part number of the screw is 6923C6 with the dimensions as DIAM 6X100-16.

I was planning to buy something from a local hardware store if someone can help me interpret the dimensions.

Thanks in advance.


  • Welcome to Motor Vehicle Maintenance & Repair! May 16 at 17:51
  • I'd be pretty sure that the 100 is actually 1.00 and the pitch of the threads.
    – dlu
    May 16 at 20:33

Was the original, or one of the others, 16 mm (about 5/8" long)? If it was, I'd read that spec as:

6mm diameter x 1.0 mm pitch x 16 mm long.

M6-1.0 is a standard size, a decent hardware store with have them. If you can take one of the other ones with you as a sample and buy two of them so that when you drop one as you install the screws and it bounces off into that place where missing bolts go to. That will only happen if you only buy the number of screws that you need to do the job.

By the way, you may not find an exact match for the head - that's ok - just match the bottom, clamping surface, of the screw. It will likely either be flat on the bottom or have the conical taper of a flat head screw.

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