Man D 2842 LE 620, Repair Manual

Page: 71 / 180

Crankshaft gaskets
69
General information on crankshaft seals
As a general principle, the radial shaft sealing rings are made of polytetrafluorothylene (PTFE), otherwise
known as Teflon.
PTFE sealing rings differ from the elastomer sealing rings that used to be common in that they have a
much wider, flat sealing lip that is not pretensioned by a coiled spring expander.
The relatively large pretension of the sealing lip itself means that it curves inwards. This is why the PTFE
sealing ring is delivered on a transport sleeve. So that it remains possible to mount the sealing ring, it must
stay on this sleeve until assembly. This applies also because the sealing lip is very sensitive and the
smallest damage causes leaks.
The sealing lip and the bearing race of the flywheel must not be coated with oil or other lubricants.
On fitting the new sealing ring, always replace the bearing race alongside it.
Assembly instructions for crankshaft seals
D
The PTFE sealing ring must be fitted absolutely free of oil and grease. Even the slightest traces of oil on
the bearing race or sealing ring will cause leakage
D
Clean oil, grease and corrosion protection agents from the bearing race before assembly. All standard
cleaning agents can be used here
D
If the PTFE sealing ring is soiled with oil or grease, it is unusable. Cleaning is not permitted in this in-
stance
D
The PTFE sealing ring must never be stored without the supplied transport sleeve. Even after it has
been stored for a period of only 30 minutes without the transport sleeve, it will lose it pretension and
thus be rendered unusable