Presta valve core
 

Yesterday I was removing the plastic cap out of a presta valve to pump in some air since tire pressure was low.
When I unscrewed the cap, the valve core came out together :lol: and tire got all deflated.

I just removed the cap from the core, or core out of the cap and screwed by hand as tight as I could to the valve stem.
Is that enough or should it be screwed with some tool?

I just inflated the tire back to 90 psi and will check later if somehow is leaking (the reliable saliva check told me is not leaking).

It wouldn't hurt to snug the core up a little. If you are careful, use a pair pliers or better, small crescent wrench. I've had that happen, sorta, the core was loose causing the tire to go flat. Discovered this after looking for a puncture!

yea I prefer fixed core tubes for that reason.. not removable core..

I've never had a removable core come out on me. But, as SJX426 suggests you can snug them up with an adjustable wrench.

I don't pay much attention for removable or not, although I'd prefer removable on tubulars where one can't simply replace a tube, or one might wish to add sealant.

There are valve removal and installation tools, very handy if you want to run sealant in your PV tire or tube.

You can best solve your problem by not using caps in the first place. The little brass nut on the valve seals the valve as well as can be. It's not like a Schrader valve which is held closed largely by spring pressure.

The only purpose a cap on a Presta tube has for me to is to keep the valve tip from chafing the tube when it's rolled up in the box or my back pocket.

I keep caps on my valves, both Presta and Schrader, to keep out dirt/grit which could keep the valve from sealing properly.

I had one come out a couple of days ago too. First time for me. I just screwed it back in and snugged it up with pliers. I replaced the cap, but not as tightly as before.

I use Lezyne mini and floor pumps and the valve cores occasionally came out when removing the threaded pump hose. Really deflating feeling (pun intended). But removable cores make adding sealant slightly easier than having a fixed valve core.