Hi, 16v.
The sleeve needs to be pressed back down into place.
There are (2) things to consider here.
1 - why did the sleeve back-out, is it loose. Normal sleeve/bore interference fit is .003 - .005"
If you want to be perfectionist about it, have a cylinder shop properly fit this sleeve or resleeve with
turned-down/fitted sleeve or replace entire cylinder assembly.
2 The band-aid approach: You can press it back into place. If the fit is loose, that cyl will run hot, poor heat transfer. Ensire that the dowel pin clearance notch on the sleeve lip is centered about the dowel pin opening.
If you want to band-aid this, then:
Thoroughly clean the cyl assembly, especially around the raised area, don't want anything trapped under there.
Put the cyl assy in the oven, upright, on blocks so the sleeves hang down and at least 1/4" above oven grill or bottom (for clearance)
Heat oven at 350 degrees for about 1/2 hour.
If the sleeve is a light interference fit, it will just drop right in. Else, you may have to gently tap it down with a soft mallet. Double check dowel pin notch alignment. While this is hot, the other sleeve may loosen-up, so don't disturb it.
Turn-off oven. Place something flat and heavy, about 5 lbs, on top of the cyl assy. This is to ensure the sleeves won't creep out during cool-down.
Cool-down for an hour or 2. Check fit.
Use new headgasket, that and the dowel pin will keep the sleeve in place.
