From model '83
OVERHAULING BRAKE
MASTER CYLINDER

Remove tandem brake master cylinder - see
34 31 000.
Replacement parts are not available for brake
master cylinder with a recessed stop pin
(ABS).


34 31 000

Important!
Use repair kit:
(1) spring, (2) support, (3) primary cup,
(4) fill-in washer, (5) intermediate piston,
(6) separating cup, (7) stop sleeve, (8) spring,
(9) screw, (10) push rod piston, (11) stop
washer, (12) secondary cup, (13) plastic
bushing, (14) circlip, (15) seal, (16) aluminum
seal and (17) silicone grease.

Apply light pressure on push rod piston (10),
lift out circlip (14) and unscrew stop screw
(18).
Release push rod piston (10) slowly and pull
out.

Knock out intermediate piston by knocking
housing on a piece of wood lightly.
Clean cylinder housing and other parts not
contained in the repair kit with alcohol and
dry with compressed air.
Tandem brake master cylinders with surfaces
damage in the cylinder bore may not be reused.
Check whether all connecting, compensating
and feeding bores are clean.

Give cylinder bore a very thin coat of ATE
brake cylinder paste.
Remove large plugs from assembly sleeve.
Slide short sleeve section on long sleeve pipe
far enough that stop washer (11), secondary
cup (12), plastic bushing (13), circlip (14),
seal (15), aluminum seal (16) and silicone
grease (17) can be removed.
Remove small plugs.

Clamp cylinder housing in a vice fitted with
aluminum jaws.
Guide assembly sleeve with long sleeve pipe
into cylinder bore.

Push stepped short sleeve pipe into cylinder
bore against shoulder and hold.

Push contents of assembly sleeve into cylinder
bore carefully with a suitable mandrel until the
intermediate piston touches the bottom of the
cylinder.

Hold intermediate piston against stop firmly
and screw in screw (18) with a new aluminum
ring (16).
Tighten stop screw (18) with a torque of
5 to 8 Nm (3.7 to 5.7 ft. Ibs.).

Let push rod piston (10) come back carefully.
Push on stop washer (11).
Coat secondary cup (12) with silicone grease
and install.
Let short stepped section of assembly sleeve
protrude and slide it over secondary clip (12),
while holding cup with two fingers.

Adjust secondary cup flush with long sleeve
pipe and push complete assembly sleeves
into cylinder bore.
Push in long sleeve pipe carefully up to point
of resistance.

Hold long sleeve pipe and pull back short
sleeve section.
Remove complete assembly sleeve.
Give plastic bushing (13) a light coat of
silicone grease and push it on push rod piston
in cylinder bore.

Press in push rod piston (10) and plastic
bushing (13).
Install circlip (14) with a special circlip pliers.
Circlip must have perfect seat in groove of
cylinder bore.
Install new seal (15) before mounting on the
brake booster.