RP23. I run it at 140psi normally. Symptoms at the moment – pump it up to 140psi and ride for about half an hour as sag increases. Attach pump and it’s down to about 30psi, so losing air fast.
Thinking about a service kit. This contains new seals and happy to do the job myself, but a couple of concerns. Having removed the air sleeve I can now see a couple of tiny (really small) scratches on the shock shaft. I think I can also feel tiny roughness on the quad seal inside the lower end of the air sleeve. I’m thinking if it was the tiny scratches that caused this roughness then new seals will only work for a short time until they too are damaged. Not sure this small a scratch would result in such huge pressure loss either.
I’m no expert so seeking some advice before sending the whole unit off to professionals.
Anyone got experience here? Thanks for your help.

Check the valve core is tight first, then if it’s OK put the shock in a bowl of water to see where it’s leaking,
If it is the scoring you might be able to repair it with some fine emery cloth and some nail varnish, if not it’ll need a new shaft

Thanks Khani. Not sure how to check valve core for tightness. I’ve prodded the pin in the middle of the valve and it moves slightly from side to side, is that evidence of it being loose, in which case how can I tighten it?

Yup, verify where the leak is coming from first. Then try installing a new seal kit. The seal and wiper on the outside only seal off the negative air chamber. It’s the inner seal at the top of the damper tube that keeps the pressure in the air can.

Personally, in preference to emery cloth I’d use something like 1200 wet and dry with soapy water to remove anything surface imperfections.

Good luck.

You need a valve core tool. Some car dustcaps have them built in.

Long nose pliers, and don’t over tighten it just nip it up,
Lefty loosey righty tighty..

Thanks to all for the useful advice. Among the options I’m looking at, one is to buy a cheap(ish) replacement. I’m a bit confused about the sizing though. I’ve measured the shock and have the following lengths; Eye-to-eye 190mm and shaft length (may not actually be technically known as shaft) 70mm. Looking on CRC there are loads of potential shocks but nothing with the 70mm length, they all seem to be commonly 50mm or 57mm. Can anyone explain this second dimension since it will affect the suspension travel. Thanks again for your wisdom.

What bike is it on?

A 2010 Canyon Nerve XC F8. I’ve got the user manual but it doesn’t specify the size of the shock.

190 x 51 according to google.

According to the Canyon website it’s a 190 eye to eye with a 50-51mm stroke so a pretty standard size
Let the air out and see how much stroke it uses when you sit on it and bottom it out, don’t bounce up and down just sit on it, a zip tie on the shaft will help you see how much it compresses
If you get a new shock you’ll need the same compression and rebound tune on the damping, normally L M H (low medium high)
If you’re happy with the shock you have a service will see it as good as new for less than a hundred quid and opens up the possibility of a custom tune that suits you sir..