valve core blocked

[TimBB]

I'm new to running tubeless. One tyre is fully inflated but the valve is blocked and won't let air in or out.
I presume I need to unscrew the valve core and replace. Seeing as it's fully inflated will the core just shoot out as the speed of sound? Is that a problem? Will all of the goo shoot out as well?
Any advice would be welcome.

[AlasdairMc]

Keep the valve at the top of the wheel so the sealant flows down to the bottom. It shouldn’t escape as a result. Give the valve core a clean, as there may be some sealant solidified that is causing the blockage.

[TheBrownDog]

Happens all the time and is one of the fun things about toobless. If you unscrew the valve core while the tyre is fully inflated it will turn into a tiny missile and shoot across your kitchen, embedding itself somewhere you will never find it. Ever. So put a small clothe over it while you unscrew it and catch it when it rockets off.

I've cleaned the values out with boiling water in the past. Works well with Stans Sealant, and for more solid mess, bit of white spirit.

[lune ranger]

The valve core will come out at fairly high speed but not like a bullet.
I’m presuming it’s presta.
I often remove the valve on an inflated tyre to deflate it when removing it.
Road or MTB? Higher pressure = higher speed - obviously. I use a removal tool and holding on to the valve is easy. My guess is that if you just use pliers it’ll be harder to control.
Have the valve at the 12 o’c position and it’ll shoot st the floor not across the room if you loose it. This will help keep the sealant in.
Replacement valve inners cost hardly anything if you buy bulk online.
Once you take your valve off you should be able to clean the whole thing up. But go ahead and buy a bunch of spares.
I carry one in my on mine tool kit.

[ChrisF]

Keep the valve at the top of the wheel, sealant will run to the bottom. Unscrew the core slowly, air should start to escape before it’s fully unscrewed. Once most of the pressure is gone you can remove the core.

[TimBB]

Thanks folks.
As I suspected, nice to have confirmation.
I'll have local eye hospital on standby......

[Bearlegged]

If you undo it a bit, it'll probably start leaking air (and reducing the the pressure) before it's unscrewed enough to achieve missile status.

[jameso]

I presume I need to unscrew the valve core and replace.

I've cleaned them out by heating the 'air in' end with a lighter gently, holding the other end (the inside rim end)- and dropping it as it gets too hot to hold - as a way of not melting the rubber seal. Works every time (so far) and seems like an easy field-fix as I always have a lighter on trips for the stove.

[Andiphim]

When storing my bike I always keep the valve at the bottom of the wheel, so any sealant in the valve runs out.
I don't think there is enough sealant in the tyre to reach the valve if it's at the bottom of the wheel.

[DickieH]

Have a new or clean inner ready. If you unscrew the inner fairly quickly, as soon as you remove the inner, stick a thumb over the outer to stop most of the air escaping.

Clean the old one and bung into spares.