what the groove in spacer sleeve (balance shaft) is for?

[wwdwgs]

Hi, all
I'm in a process of replacing front end seals/ gaskets/ water pump.
After removing Spacer Sleeve (928 105 139 02) I noticed an internal groove.
See attached picture.
What is it for? O-ring? Leave empty? According to PET katolog, there is no o-ring.
This groove is on spacer sleeves for both balance shaft and cam shaft.
Let me know.

[walfreyydo]

Inner internal groove (as indicated in your photo) is normal per the Pelican guide:
https://www.pelicanparts.com/techarticles/Porsche_944_Turbo/67-ENGINE-Balance_Shaft_Seals_Replacment/67-ENGINE-Balance_Shaft_Seals_Replacment.htm
(See Figure 9)

A groove on the outside is not normal (but common and is from the plastic seal wearing into the metal sleeve), which is why you should replace that metal sleeve in your photo with a new one along with a new seal.

[OK-944]

That groove in the spacer sleeve is an oil groove...which receives oil from the hole in the balance shaft and helps to keep that end of the shaft lubricated. Go to walfreyydo's link above, and look closely at photo #5 and you'll see the hole in the shaft.

So don't look for an O-ring for this groove if you are doing a reseal...because you won't find one - which is a good thing!

[wwdwgs]

Thank you, guys.