come loose. They pull out of the hole and eventually go missing after rolling into the engine bay somewhere.
If you haven't lost the fastener, you can hold it back in place with a thin 5mm nylon washer which is what
is fitted as standard. Alternatively you could fit a 6mm star retaining washer or a 5mm e-clip (c-clip, circlip).
However, the original engine bay fixings are rolled, not machined. They aren't as smooth to operate and
corrosion can make them stiff or notchy to twist, making it hard to properly close the engine bay cover.
For the price, you may as well replace the fastener with a new one that is well made.
Smartmods.co.uk sell machined fasteners made by the company that invented them, no crap copies.
What they sell is the official 17mm Dzus Panex fixing kit as seen below.
Lever out the old retainer. The old one won't be as springy as the replacement.
Slide the new retainer into position.
Put the new quarter turn fastener into the hole of the engine bay lid...
...and then push the nylon washer onto the back to hold it in place.
The quarter turn fastener is now correctly set in place and ready to hold the engine bay lid down.
I recommend a little copper grease on the stem of the fastener to keep the action smooth.