Valve Stem Oil Seals - BMW 5251 Service Manual

Table d. Valve guide specifications
Specifications
All
engines (1997-2002)
Valve guide wear, maximum
0.5 mrn (0.020 in)
(valve tilt clearance measured
with new valve)
Valve guide inside diameter, installed
(tolerance per IS0 allowance
H7)
Standard 6.0 mm (0.236 in)
Oversize 1
6.1 mrn (0.240 in)
Oversize 2
6.2 mm (0.244 in)
Valve stem oil seals
The purpose of the valve stem oil seal is to prevent excess oil
from entering the combustion chamber. The sign of faulty
valve stem oil seals is excessive oil consumption and smoke
from the exhaust immediately after starting and during decel-
eration.
NOTE-
Valve stem oil seals should not be reused. I f valves are re-
moved, new valve stem oil seals should be installed.
Valve stem oil seal replacement requires that the cylinder
head be disassembled and the valves removed as described
above under Valves, removing and installing.
NOTE-
BMW special tools are available to remove the valve stem oil
seals. As an alternative, standard valve seal removal tools
are available from most automotive parts stores.
Lubricate new seal and install using hand pressure only. Be
sure to install valve spring seat(s) before installing seal.